The dma_cache_sync routines is used to flush caches for memory returned by dma_alloc_attrs with the DMA_ATTR_NON_CONSISTENT flag (or previously from dma_alloc_noncoherent), but the requirements for it seems to be frequently misunderstood. dma_cache_sync is documented to be a no-op for allocations that do not have the DMA_ATTR_NON_CONSISTENT flag set, and yet a lot of architectures implement it in some way despite not implementing DMA_ATTR_NON_CONSISTENT. This series removes a few abuses of dma_cache_sync for non-DMA API purposes, then changes all remaining architectures that do not implement DMA_ATTR_NON_CONSISTENT to implement dma_cache_sync as a no-op, and then adds the struct dma_map_ops indirection we use for all other DMA mapping operations to dma_cache_sync as well, thus removing all but two implementations of the function.
