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>

arch/xtensa/kernel/vectors.S

@@ -46,7 +46,7 @@
 #include <asm/ptrace.h>
 #include <asm/ptrace.h>
 #include <asm/current.h>
-#include <asm/offsets.h>
+#include <asm/asm-offsets.h>
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 #include <asm/page.h>