scsi: isci: use dma_set_mask_and_coherent

The driver currently uses pci_set_dma_mask despite otherwise using the
generic DMA API.  Switch it over to the better generic DMA API.

[mkp: s/iscsi/isci/]

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