ALSA: atmel - Fix the return value in error path

In the commit c0763e68
    ALSA: snd-atmel-abdac: test wrong variable
the return value via PTR_ERR() had to be fixed as well.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/atmel/abdac.c

@@ -422,7 +422,7 @@ static int __devinit atmel_abdac_probe(struct platform_device *pdev)
 	sample_clk = clk_get(&pdev->dev, "sample_clk");
 	if (IS_ERR(sample_clk)) {
 		dev_dbg(&pdev->dev, "no sample clock\n");
-		retval = PTR_ERR(pclk);
+		retval = PTR_ERR(sample_clk);
 		goto out_put_pclk;
 	}
 	clk_enable(pclk);