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/ppc/kernel/head.S b/arch/ppc/kernel/head.S
index a931d77..55daf12 100644
--- a/arch/ppc/kernel/head.S
+++ b/arch/ppc/kernel/head.S
@@ -31,7 +31,7 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 #include <asm/ppc_asm.h>
-#include <asm/offsets.h>
+#include <asm/asm-offsets.h>
 
 #ifdef CONFIG_APUS
 #include <asm/amigappc.h>