The implemementation for the CONFIG_NOT_COHERENT_CACHE case doesn't share
any code with the one for systems with coherent caches.  Split it off
and merge it with the helpers in dma-noncoherent.c that have no other
callers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>