s390/pfault: use UL instead of ULL

Remove another leftover of the 31 bit area: replace the not needed
"unsigned long long" suffix with "unsigned long", and stay consistent
with the rest of the code.

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>