We observed a large(order-3) allocation in evdev_open() and it may
cause an OOM kernel panic in kzalloc(), before we getting to the
vzalloc() fallback.

Fix it by converting kzalloc()/vzalloc() to kvzalloc() to avoid the
OOM killer logic as we have a vmalloc fallback.

InputReader invoked oom-killer: gfp_mask=0x240c2c0
(GFP_KERNEL|__GFP_NOWARN|__GFP_COMP|__GFP_ZERO), nodemask=0, order=3,
oom_score_adj=-900
...
(dump_backtrace) from (show_stack+0x18/0x1c)
(show_stack) from (dump_stack+0x94/0xa8)
(dump_stack) from (dump_header+0x7c/0xe4)
(dump_header) from (out_of_memory+0x334/0x348)
(out_of_memory) from (__alloc_pages_nodemask+0xe9c/0xeb8)
(__alloc_pages_nodemask) from (kmalloc_order_trace+0x34/0x128)
(kmalloc_order_trace) from (__kmalloc+0x258/0x36c)
(__kmalloc) from (evdev_open+0x5c/0x17c)
(evdev_open) from (chrdev_open+0x100/0x204)
(chrdev_open) from (do_dentry_open+0x21c/0x354)
(do_dentry_open) from (vfs_open+0x58/0x84)
(vfs_open) from (path_openat+0x640/0xc98)
(path_openat) from (do_filp_open+0x78/0x11c)
(do_filp_open) from (do_sys_open+0x130/0x244)
(do_sys_open) from (SyS_openat+0x14/0x18)
(SyS_openat) from (__sys_trace_return+0x0/0x10)
...
Normal: 12488*4kB (UMEH) 6984*8kB (UMEH) 2101*16kB (UMEH) 0*32kB
0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 139440kB
HighMem: 206*4kB (H) 131*8kB (H) 42*16kB (H) 2*32kB (H) 0*64kB
0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 2608kB
...
Kernel panic - not syncing: Out of memory and no killable processes...
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>