mxs/spi: fix error return code in mxs_spi_probe()

Fix to return a negative error code from the error handling
case instead of 0, as returned elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c
index 22a0af0..a1d5778 100644
--- a/drivers/spi/spi-mxs.c
+++ b/drivers/spi/spi-mxs.c
@@ -612,6 +612,7 @@
 	ssp->dmach = dma_request_channel(mask, mxs_ssp_dma_filter, ssp);
 	if (!ssp->dmach) {
 		dev_err(ssp->dev, "Failed to request DMA\n");
+		ret = -ENODEV;
 		goto out_master_free;
 	}