s390/kernel: convert SYSCALL and PGM_CHECK handlers to .quad

With a relocatable kernel that could reside at any place in memory, the
storage size for the SYSCALL and PGM_CHECK handlers needs to be
increased from .long to .quad.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>