kbuild: clean up scripts/headers.sh

'drop' variable is unused.

'ppc' and 'sparc64' directories don't exist in arch/,
and I think their headers can be well exported now, so
just remove them.
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/headers.sh

@@ -15,19 +15,12 @@ do_command()
 	fi
 }
 
-# Do not try this architecture
-drop="generic um ppc sparc64 cris"
-
 archs=$(ls ${srctree}/arch)
 
 for arch in ${archs}; do
 	case ${arch} in
 	um)        # no userspace export
 		;;
-	ppc)       # headers exported by powerpc
-		;;
-	sparc64)   # headers exported by sparc
-		;;
 	cris)      # headers export are known broken
 		;;
 	*)