scsi: qla2xxx: Use zeroing allocator rather than allocator/memset

Use dma_zalloc_coherent and vzalloc instead of dma_alloc_coherent and
vmalloc respectively, followed by memset 0.

Generated-by: scripts/coccinelle/api/alloc/kzalloc-simple.cocci

Suggested-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>