common: dma-mapping: introduce generic alloc() and free() methods

Introduce new generic alloc and free methods with attributes argument.

Existing alloc_coherent and free_coherent can be implemented on top of the
new calls with NULL attributes argument. Later also dma_alloc_non_coherent
can be implemented using DMA_ATTR_NONCOHERENT attribute as well as
dma_alloc_writecombine with separate DMA_ATTR_WRITECOMBINE attribute.

This way the drivers will get more generic, platform independent way of
allocating dma buffers with specific parameters.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: David Gibson <david@gibson.dropbear.ud.au>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

include/linux/dma-mapping.h

@@ -13,6 +13,12 @@ struct dma_map_ops {
 				dma_addr_t *dma_handle, gfp_t gfp);
 	void (*free_coherent)(struct device *dev, size_t size,
 			      void *vaddr, dma_addr_t dma_handle);
+	void* (*alloc)(struct device *dev, size_t size,
+				dma_addr_t *dma_handle, gfp_t gfp,
+				struct dma_attrs *attrs);
+	void (*free)(struct device *dev, size_t size,
+			      void *vaddr, dma_addr_t dma_handle,
+			      struct dma_attrs *attrs);
 	dma_addr_t (*map_page)(struct device *dev, struct page *page,
 			       unsigned long offset, size_t size,
 			       enum dma_data_direction dir,