misc/genwqe: ensure zero initialization

Genwqe uses dma_alloc_coherent and depends on zero initialized memory. On
one occasion it ueses an explicit memset on others it uses un-initialized
memory.

This bug was covered because some archs actually return zero initialized
memory when using dma_alloc_coherent but this is by no means guaranteed.
Simply switch to dma_zalloc_coherent.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/genwqe/card_ddcb.c

@@ -1048,8 +1048,6 @@ static int setup_ddcb_queue(struct genwqe_dev *cd, struct ddcb_queue *queue)
 			"[%s] **err: could not allocate DDCB **\n", __func__);
 		return -ENOMEM;
 	}
-	memset(queue->ddcb_vaddr, 0, queue_size);
-
 	queue->ddcb_req = kzalloc(sizeof(struct ddcb_requ *) *
 				  queue->ddcb_max, GFP_KERNEL);
 	if (!queue->ddcb_req) {