scsi: mpt3sas: Remove superfluous memset()

Fixes coccicheck warning:

./drivers/scsi/mpt3sas/mpt3sas_base.c:5247:16-34: WARNING: dma_alloc_coherent use in ioc -> request already zeroes out memory,  so memset is not needed

dma_alloc_coherent() already zeroes out memory so memset() is not needed.

Link: https://lore.kernel.org/r/1596079918-41115-4-git-send-email-liheng40@huawei.com


Signed-off-by: Li Heng <liheng40@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>