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>

arch/arm/mm/tlb-v6.S

@@ -11,7 +11,7 @@
  *  These assume a split I/D TLB.
  */
 #include <linux/linkage.h>
-#include <asm/constants.h>
+#include <asm/asm-offsets.h>
 #include <asm/page.h>
 #include <asm/tlbflush.h>
 #include "proc-macros.S"