scsi: pmcraid: don't allocate a dma coherent buffer for sense data

We can just dma map the sense buffer passed with the scsi command,
and that gets us out of the nasty business of doing dma coherent
allocations from irq context.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>