[PATCH] s390: fstatat64 support

Add fstatat64 support to s390 in order to follow changes with
commit cff2b760 .
Also fixes compilation for 31 bit.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>