DMA-API: media: omap3isp: use dma_coerce_mask_and_coherent()

The code sequence:
	isp->raw_dmamask = DMA_BIT_MASK(32);
	isp->dev->dma_mask = &isp->raw_dmamask;
	isp->dev->coherent_dma_mask = DMA_BIT_MASK(32);
bypasses the architectures check on the DMA mask.  It can be replaced
with dma_coerce_mask_and_coherent(), avoiding the direct initialization
of this mask.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>