s390/cio: Restore GFP_DMA for CHSC allocation

s390/cio: Restore GFP_DMA for CHSC allocation

Re-add GFP_DMA when allocating memory for CHSC control blocks.
On some supported machines, CHSC cannot access memory outside
the DMA zone, causing CHSC command failures.

Cc: stable@vger.kernel.org
Fixes: a3a64a4def8d ("s390/cio: remove unneeded DMA zone allocation")
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>