ALSA: atmel - Fix the return value in error path

In the commit c0763e687d0283d0db507813ca4462aa4073c5b5
    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>
diff --git a/sound/atmel/abdac.c b/sound/atmel/abdac.c
index 4e47baad..6e24091 100644
--- a/sound/atmel/abdac.c
+++ b/sound/atmel/abdac.c
@@ -422,7 +422,7 @@
 	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);