[PATCH] s390: merge common parts of head.S and head64.S

Merge common parts of head.S and head64.S into head.S and move architecture
specific parts to head31.S and head64.S respectively.  Saves us ~500 lines
of duplicated assembly code.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>