DMA-API: net: b43legacy: replace dma_set_mask()+dma_set_coherent_mask() with new helper

Replace the following sequence:

	dma_set_mask(dev, mask);
	dma_set_coherent_mask(dev, mask);

with a call to the new helper dma_set_mask_and_coherent().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>