[ARM] Provide dummy noncoherent DMA API

We don't currently support the noncoherent DMA API, but it needs to
be provided for kernels with devres to link.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/asm-arm/dma-mapping.h

@@ -61,6 +61,22 @@ static inline int dma_mapping_error(dma_addr_t dma_addr)
 	return dma_addr == ~0;
 }
 
+/*
+ * Dummy noncoherent implementation.  We don't provide a dma_cache_sync
+ * function so drivers using this API are highlighted with build warnings.
+ */
+static inline void *
+dma_alloc_noncoherent(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
+{
+	return NULL;
+}
+
+static inline void
+dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr,
+		     dma_addr_t handle)
+{
+}
+
 /**
  * dma_alloc_coherent - allocate consistent memory for DMA
  * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices