dma-mapping: dma-mapping.h: add dma_set_coherent_mask

dma_set_coherent_mask corresponds to pci_set_consistent_dma_mask.  This is
necessary to move to the generic device model DMA API from the PCI bus
specific API in the long term.

dma_set_coherent_mask works in the exact same way that
pci_set_consistent_dma_mask does.  So this patch also changes
pci_set_consistent_dma_mask to call dma_set_coherent_mask.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@suse.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>