scsi: snic: Use vzalloc

Replaced vmalloc + memset with vzalloc

Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@gmail.com>
Acked-by: Sesidhar Baddela <sebaddel@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>