metag: Provide dma_get_sgtable()

metag/allmodconfig:

drivers/media/v4l2-core/videobuf2-dma-contig.c: In function 'vb2_dc_get_base_sgt':
drivers/media/v4l2-core/videobuf2-dma-contig.c:387: error: implicit declaration of function 'dma_get_sgtable'

For architectures using dma_map_ops, dma_get_sgtable() is provided in
<asm-generic/dma-mapping-common.h>.

Metag does not use dma_map_ops yet, hence it should implement it as an
inline stub using dma_common_get_sgtable().
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

arch/metag/include/asm/dma-mapping.h

@@ -180,4 +180,11 @@ dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 {
 }
 
+/* drivers/base/dma-mapping.c */
+extern int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
+				  void *cpu_addr, dma_addr_t dma_addr,
+				  size_t size);
+
+#define dma_get_sgtable(d, t, v, h, s) dma_common_get_sgtable(d, t, v, h, s)
+
 #endif