checkstack: add loongarch support for scripts/checkstack.pl

scripts/checkstack.pl lacks support for the loongarch architecture.  Add
support to detect "addi.{w,d} $sp, $sp, -FRAME_SIZE" stack frame
generation instruction.

Link: https://lkml.kernel.org/r/MW4PR84MB314514273F0B7DBCC5E35A978192A@MW4PR84MB3145.NAMPRD84.PROD.OUTLOOK.COM


Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>