s390/ctlreg: add type checking to __local_ctl_load() and __local_ctl_store()

Add type checking to __local_ctl_load() and __local_ctl_store(). For
both functions enforce to pass an array consisting of unsigned longs.

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>