MIPS: Add DMA declare coherent memory support

The ohci-sm501 driver requires dma_declare_coherent_memory().  It is used
by the driver's local memory allocation with dma_alloc_coherent().

Tested on TANBAC TB0287(VR4131 + SM501).

[Ralf: Fixed reject in dma-default.c and removed the entire #if 0'ed block
 in dma-mapping.h instead of just the #if 0.]

Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/dma-default.c

@@ -90,6 +90,9 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
 {
 	void *ret;
 
+	if (dma_alloc_from_coherent(dev, size, dma_handle, &ret))
+		return ret;
+
 	gfp = massage_gfp_flags(dev, gfp);
 
 	ret = (void *) __get_free_pages(gfp, get_order(size));
@@ -122,6 +125,10 @@ void dma_free_coherent(struct device *dev, size_t size, void *vaddr,
 	dma_addr_t dma_handle)
 {
 	unsigned long addr = (unsigned long) vaddr;
+	int order = get_order(size);
+
+	if (dma_release_from_coherent(dev, order, vaddr))
+		return;
 
 	plat_unmap_dma_mem(dev, dma_handle, size, DMA_BIDIRECTIONAL);