kbuild: arm - use generic asm-offsets.h support

Delete obsoleted stuff from arch Makefile and rename
constants.h to asm-offsets.h

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/arch/arm/lib/putuser.S b/arch/arm/lib/putuser.S
index b09398d..4593e9c 100644
--- a/arch/arm/lib/putuser.S
+++ b/arch/arm/lib/putuser.S
@@ -26,7 +26,7 @@
  * Note that ADDR_LIMIT is either 0 or 0xc0000000
  * Note also that it is intended that __put_user_bad is not global.
  */
-#include <asm/constants.h>
+#include <asm/asm-offsets.h>
 #include <asm/thread_info.h>
 #include <asm/errno.h>