scsi: lpfc: Use dma_zalloc_coherent

Replaced dma_alloc_coherent + memset with dma_zalloc_coherent.

Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@gmail.com>
Acked-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>