kbuild: m68k,parisc,ppc,ppc64,s390,xtensa use generic asm-offsets.h support

Delete obsoleted parts form arch makefiles and rename to asm-offsets.h

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index c64a01f..5c018c5 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -14,7 +14,7 @@
  */
 
 #include <linux/linkage.h>
-#include <asm/offsets.h>
+#include <asm/asm-offsets.h>
 #include <asm/processor.h>
 #include <asm/thread_info.h>
 #include <asm/uaccess.h>