sh: make dma_cache_sync a no-op

sh does not implement DMA_ATTR_NON_CONSISTENT allocations, so it doesn't
make any sense to do any work in dma_cache_sync given that it
must be a no-op when dma_alloc_attrs returns coherent memory.

On the other hand sh uses dma_cache_sync internally in the dma_ops
implementation and for the maple bus that does not use the DMA API,
so a the old functionality for dma_cache_sync is still provided under
the name sh_sync_dma_for_device, and without the redundant dev
argument.  While at it two of the syncing dma_ops also go the proper
_for_device postfix.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>