sh: Add dma-mapping support for dma_alloc/free_coherent() overrides.

This moves the current dma_alloc/free_coherent() calls to a generic
variant and plugs them in for the nommu default. Other variants can
override the defaults in the dma mapping ops directly.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/kernel/dma-nommu.c b/arch/sh/kernel/dma-nommu.c
index e88fceb..b336fcf 100644
--- a/arch/sh/kernel/dma-nommu.c
+++ b/arch/sh/kernel/dma-nommu.c
@@ -61,6 +61,8 @@
 }
 
 struct dma_map_ops nommu_dma_ops = {
+	.alloc_coherent		= dma_generic_alloc_coherent,
+	.free_coherent		= dma_generic_free_coherent,
 	.map_page		= nommu_map_page,
 	.map_sg			= nommu_map_sg,
 	.sync_single_for_device	= nommu_sync_single,