s390/mm: Allow large pages only for aligned physical addresses

Do not allow creation of large pages against physical addresses,
which itself are not aligned on the correct boundary. Failure to
do so might lead to referencing wrong memory as result of the way
DAT works.

Fixes: c98d2eca ("s390/mm: Uncouple physical vs virtual address spaces")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>