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: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi-mxs.c

@@ -612,6 +612,7 @@ static int mxs_spi_probe(struct platform_device *pdev)
 	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;
 	}