scsi: hisi_sas: Drop SMP resp frame DMA mapping

The SMP frame response is written to the command table and not the SMP
response pointer from libsas, so don't bother DMA mapping (and unmapping)
the SMP response from libsas.

Suggested-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>