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/[e-mail]
Signed-off-by: Youling Tang <[e-mail]>
Acked-by: Huacai Chen <[e-mail]>
Cc: John Paul Adrian Glaubitz <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

scripts/checkstack.pl

···
 #	sparc port by Martin Habets <[e-mail]>
 #	ppc64le port by Breno Leitao <[e-mail]>
 #	riscv port by Wadim Mueller <[e-mail]>
+#	loongarch port by Youling Tang <[e-mail]>
 #
 #	Usage:
 #	objdump -d vmlinux | scripts/checkstack.pl [arch]
···
 	} elsif ($arch =~ /^riscv(64)?$/) {
 		#ffffffff8036e868:	c2010113          	addi	sp,sp,-992
 		$re = qr/.*addi.*sp,sp,-(([0-9]{2}|[3-9])[0-9]{2})/o;
+	} elsif ($arch =~ /^loongarch(32|64)?$/) {
+		#9000000000224708:	02ff4063		addi.d  $sp, $sp, -48(0xfd0)
+		$re = qr/.*addi\..*sp, .*sp, -([0-9]{1,8}).*/o;
 	} else {
 		print("wrong or unknown architecture \"$arch\"\n");
 		exit