tags: Use $SRCARCH

$ make mrproper
$ make tags
GEN tags
find: `arch/x86_64/': No such file or directory

Caused by commit f81b1be (tags: include headers before source files)

Cc: Guennadi Liakhovetski <[e-mail]>
Acked-by: WANG Cong <[e-mail]>
Signed-off-by: Michal Marek <[e-mail]>

scripts/tags.sh

···
 # mode may be any of: tags, TAGS, cscope
 #
 # Uses the following environment variables:
-# ARCH, SUBARCH, srctree, src, obj
+# ARCH, SUBARCH, SRCARCH, srctree, src, obj
 
 if [ "$KBUILD_VERBOSE" = "1" ]; then
 	set -x
···
 
 all_sources()
 {
-	find_arch_include_sources ${ARCH} '*.[chS]'
+	find_arch_include_sources ${SRCARCH} '*.[chS]'
 	if [ ! -z "$archinclude" ]; then
 		find_arch_include_sources $archinclude '*.[chS]'
 	fi