Switch from the legacy PCI DMA API to the generic DMA API.

Also reuse an existing helper (after fixing the error return) to set the
DMA mask instead of having three copies of the code.

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