To avoid NULL function pointer access. This happens on VG10, reboot
command hangs and have to power off/on to reboot the machine. This is
serial console log:

[  OK  ] Reached target Unmount All Filesystems.
[  OK  ] Reached target Final Step.
         Starting Reboot...
[  305.696271] systemd-shutdown[1]: Syncing filesystems and block
devices.
[  306.947328] systemd-shutdown[1]: Sending SIGTERM to remaining
processes...
[  306.963920] systemd-journald[1722]: Received SIGTERM from PID 1
(systemd-shutdow).
[  307.322717] systemd-shutdown[1]: Sending SIGKILL to remaining
processes...
[  307.336472] systemd-shutdown[1]: Unmounting file systems.
[  307.454202] EXT4-fs (sda2): re-mounted. Opts: errors=remount-ro
[  307.480523] systemd-shutdown[1]: All filesystems unmounted.
[  307.486537] systemd-shutdown[1]: Deactivating swaps.
[  307.491962] systemd-shutdown[1]: All swaps deactivated.
[  307.497624] systemd-shutdown[1]: Detaching loop devices.
[  307.504418] systemd-shutdown[1]: All loop devices detached.
[  307.510418] systemd-shutdown[1]: Detaching DM devices.
[  307.565907] sd 2:0:0:0: [sda] Synchronizing SCSI cache
[  307.731313] BUG: kernel NULL pointer dereference, address:
0000000000000000
[  307.738802] #PF: supervisor read access in kernel mode
[  307.744326] #PF: error_code(0x0000) - not-present page
[  307.749850] PGD 0 P4D 0
[  307.752568] Oops: 0000 [#1] SMP PTI
[  307.756314] CPU: 3 PID: 1 Comm: systemd-shutdow Not tainted
5.2.0-rc1-kfd-yangp #453
[  307.764644] Hardware name: ASUS All Series/Z97-PRO(Wi-Fi ac)/USB 3.1,
BIOS 9001 03/07/2016
[  307.773580] RIP: 0010:soc15_common_hw_fini+0x33/0xc0 [amdgpu]
[  307.779760] Code: 89 fb e8 60 f5 ff ff f6 83 50 df 01 00 04 75 3d 48
8b b3 90 7d 00 00 48 c7 c7 17 b8 530
[  307.799967] RSP: 0018:ffffac9483153d40 EFLAGS: 00010286
[  307.805585] RAX: 0000000000000000 RBX: ffff9eb299da0000 RCX:
0000000000000006
[  307.813261] RDX: 0000000000000000 RSI: ffff9eb29e3508a0 RDI:
ffff9eb29e350000
[  307.820935] RBP: ffff9eb299da0000 R08: 0000000000000000 R09:
0000000000000000
[  307.828609] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff9eb299dbd1f8
[  307.836284] R13: ffffffffc04f8368 R14: ffff9eb29cebd130 R15:
0000000000000000
[  307.843959] FS:  00007f06721c9940(0000) GS:ffff9eb2a18c0000(0000)
knlGS:0000000000000000
[  307.852663] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  307.858842] CR2: 0000000000000000 CR3: 000000081d798005 CR4:
00000000001606e0
[  307.866516] Call Trace:
[  307.869169]  amdgpu_device_ip_suspend_phase2+0x80/0x110 [amdgpu]
[  307.875654]  ? amdgpu_device_ip_suspend_phase1+0x4d/0xd0 [amdgpu]
[  307.882230]  amdgpu_device_ip_suspend+0x2e/0x60 [amdgpu]
[  307.887966]  amdgpu_pci_shutdown+0x2f/0x40 [amdgpu]
[  307.893211]  pci_device_shutdown+0x31/0x60
[  307.897613]  device_shutdown+0x14c/0x1f0
[  307.901829]  kernel_restart+0xe/0x50
[  307.905669]  __do_sys_reboot+0x1df/0x210
[  307.909884]  ? task_work_run+0x73/0xb0
[  307.913914]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[  307.918970]  do_syscall_64+0x4a/0x1c0
[  307.922904]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  307.928336] RIP: 0033:0x7f0671cf8373
[  307.932176] Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00
00 0f 1f 44 00 00 89 fa be 69 19 128
[  307.952384] RSP: 002b:00007ffdd1723d68 EFLAGS: 00000202 ORIG_RAX:
00000000000000a9
[  307.960527] RAX: ffffffffffffffda RBX: 0000000001234567 RCX:
00007f0671cf8373
[  307.968201] RDX: 0000000001234567 RSI: 0000000028121969 RDI:
00000000fee1dead
[  307.975875] RBP: 00007ffdd1723dd0 R08: 0000000000000000 R09:
0000000000000000
[  307.983550] R10: 0000000000000002 R11: 0000000000000202 R12:
00007ffdd1723dd8
[  307.991224] R13: 0000000000000000 R14: 0000001b00000004 R15:
00007ffdd17240c8
[  307.998901] Modules linked in: xt_MASQUERADE nfnetlink iptable_nat
xt_addrtype xt_conntrack nf_nat nf_cos
[  308.026505] CR2: 0000000000000000
[  308.039998] RIP: 0010:soc15_common_hw_fini+0x33/0xc0 [amdgpu]
[  308.046180] Code: 89 fb e8 60 f5 ff ff f6 83 50 df 01 00 04 75 3d 48
8b b3 90 7d 00 00 48 c7 c7 17 b8 530
[  308.066392] RSP: 0018:ffffac9483153d40 EFLAGS: 00010286
[  308.072013] RAX: 0000000000000000 RBX: ffff9eb299da0000 RCX:
0000000000000006
[  308.079689] RDX: 0000000000000000 RSI: ffff9eb29e3508a0 RDI:
ffff9eb29e350000
[  308.087366] RBP: ffff9eb299da0000 R08: 0000000000000000 R09:
0000000000000000
[  308.095042] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff9eb299dbd1f8
[  308.102717] R13: ffffffffc04f8368 R14: ffff9eb29cebd130 R15:
0000000000000000
[  308.110394] FS:  00007f06721c9940(0000) GS:ffff9eb2a18c0000(0000)
knlGS:0000000000000000
[  308.119099] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  308.125280] CR2: 0000000000000000 CR3: 000000081d798005 CR4:
00000000001606e0
[  308.135304] printk: systemd-shutdow: 3 output lines suppressed due to
ratelimiting
[  308.143518] Kernel panic - not syncing: Attempted to kill init!
exitcode=0x00000009
[  308.151798] Kernel Offset: 0x15000000 from 0xffffffff81000000
(relocation range: 0xffffffff80000000-0xff)
[  308.171775] ---[ end Kernel panic - not syncing: Attempted to kill
init! exitcode=0x00000009 ]---
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>