dma: mxs-dma: Staticize mxs_dma_xlate

Fix the following sparse warning:

drivers/dma/mxs-dma.c:696:17: warning: symbol 'mxs_dma_xlate' was not declared. Should it be static?
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/mxs-dma.c

@@ -693,7 +693,7 @@ static bool mxs_dma_filter_fn(struct dma_chan *chan, void *fn_param)
 	return true;
 }
 
-struct dma_chan *mxs_dma_xlate(struct of_phandle_args *dma_spec,
+static struct dma_chan *mxs_dma_xlate(struct of_phandle_args *dma_spec,
 			       struct of_dma *ofdma)
 {
 	struct mxs_dma_engine *mxs_dma = ofdma->of_dma_data;