use the generic dma-noncoherent code for sh V3

From: Christoph Hellwig
Date: Wed Jul 25 2018 - 05:41:32 EST

Hi all,

can you review these patches to switch sh to use the generic
dma-noncoherent code? All the requirements are in mainline already
and we've switched various architectures over to it already.

Changes since V2:
- drop a now obsolete export

Changes since V1:
- fixed two stupid compile errors and verified them using a local
cross toolchain instead of the 0day buildbot