Since setup_tlb_handler() is executed in atomic context, we should use
GFP_ATOMIC instead of GFP_KERNEL to alloc pages. Otherwise we will get
a "sleeping in atomic context" error:

[    0.013118] BUG: sleeping function called from invalid context at mm/page_alloc.c:5158
[    0.013126] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
[    0.013131] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.19-rc3+ #1008 1a223086d14d07967cc427f15d52139422271360
[    0.013136] Hardware name: Loongson Loongson-3A5000-7A1000-1w-V0.1-CRB/Loongson-LS3A5000-7A1000-1w-EVB-V1.21, BIOS Loongson-UDK2018-V2.0.04082-beta7 04/27
[    0.013140] Stack : 90000000015fc990 9000000100493c18 9000000000df3370 9000000100490000
[    0.013151]         9000000100493b50 0000000000000000 9000000100493b58 9000000001417ef0
[    0.013160]         900000000199e54e 0000000000000040 9000000100493c18 90000000015f7a98
[    0.013168]         ffffffffffffffff 6de72f8b42179d1e 9000000100403b80 90000000015f7890
[    0.013176]         0000000000000001 00000000fffff175 9000000000eb9860 9000000001530b4b
[    0.013184]         9000000000e99e60 0000000000000013 0000000006ecc000 0000000000000001
[    0.013193]         90000000015f7a98 9000000001417ef0 0000000000000004 0000000000000000
[    0.013201]         0000000000000cc0 0000000000000000 0000000000000001 90000000015fc990
[    0.013209]         9000000000217e74 9000000001603b6b 9000000000208640 0000000000000000
[    0.013217]         00000000000000b0 0000000000000004 0000000000000000 0000000000070000
[    0.013225]         ...
[    0.013229] Call Trace:
[    0.013230] [<9000000000208640>] show_stack+0x4c/0x14c
[    0.013240] [<9000000000df3370>] dump_stack_lvl+0x70/0xac
[    0.013246] [<9000000000270c8c>] ___might_sleep+0x104/0x124
[    0.013253] [<9000000000477e84>] __alloc_pages+0x240/0x464
[    0.013260] [<9000000000214214>] setup_tlb_handler+0x104/0x1e8
[    0.013265] [<9000000000214324>] tlb_init+0x2c/0x3c
[    0.013270] [<9000000000208b74>] per_cpu_trap_init+0xec/0x108
[    0.013275] [<9000000000202850>] cpu_probe+0x400/0x8a4
[    0.013279] [<900000000020d160>] start_secondary+0x5c/0x3d4
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>