scsi: vmw_pvscsi: Fix swiotlb operation

scsi: vmw_pvscsi: Fix swiotlb operation

With swiotlb, the first byte of the sense buffer may in some cases be
uninitialized since we use DMA_FROM_DEVICE, and the device incorrectly
doesn't clear it. In those cases, clear it after DMA unmapping.

Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20191203193052.7583-1-thomas_os@shipmail.org
Suggested-by: Vishal Bhakta <vbhakta@vmware.com>
Acked-by: Jim Gill <jgill@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>