IB/cxgb3: Set dev.parent instead of dma_device

Prepare for removal of ib_device.dma_device.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Steve Wise <swise@chelsio.com>
Acked-by: Steve Wise <swise@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>