dma-coherent: remove the DMA_MEMORY_MAP and DMA_MEMORY_IO flags

DMA_MEMORY_IO was never used in the tree, so remove it.  That means there is
no need for the DMA_MEMORY_MAP flag either now, so remove it as well and
change dma_declare_coherent_memory to return a normal errno value.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>