i2c: mxs: Use dma_request_chan() instead dma_request_slave_channel()

dma_request_slave_channel() is a wrapper on top of dma_request_chan()
eating up the error code.

By using dma_request_chan() directly the driver can support deferred
probing against DMA.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-mxs.c

@@ -836,10 +836,10 @@ static int mxs_i2c_probe(struct platform_device *pdev)
 	}
 
 	/* Setup the DMA */
-	i2c->dmach = dma_request_slave_channel(dev, "rx-tx");
-	if (!i2c->dmach) {
+	i2c->dmach = dma_request_chan(dev, "rx-tx");
+	if (IS_ERR(i2c->dmach)) {
 		dev_err(dev, "Failed to request dma\n");
-		return -ENODEV;
+		return PTR_ERR(i2c->dmach);
 	}
 
 	platform_set_drvdata(pdev, i2c);