drm/mediatek: Fix an error code in mtk_hdmi_dt_parse_pdata()

We don't want to overwrite "ret", it already holds the correct error
code.  The "regmap" variable might be a valid pointer as this point.

Fixes: 8f83f268 ("drm/mediatek: Add HDMI support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_hdmi.c

@@ -1480,7 +1480,6 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
 	if (IS_ERR(regmap))
 		ret = PTR_ERR(regmap);
 	if (ret) {
-		ret = PTR_ERR(regmap);
 		dev_err(dev,
 			"Failed to get system configuration registers: %d\n",
 			ret);