ipr: set coherent DMA mask

Use dma_set_mask_and_coherent() to set both the DMA and coherent
DMA mask.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>