pinctrl: mediatek: fix wrong assignment in mtk_get_pin_name

This is a bug fix for mtk pinctrl common part. Appearently pins should be
used instead of grps in mtk_get_pin_name().

diff --git a/drivers/pinctrl/mediatek/pinctrl-mtk-common.c b/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
index 4dd3f73..b700dd9 100644
--- a/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
+++ b/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
@@ -219,7 +219,7 @@
 {
 	struct mtk_pinctrl_priv *priv = dev_get_priv(dev);
 
-	if (!priv->soc->grps[selector].name)
+	if (!priv->soc->pins[selector].name)
 		return mtk_pinctrl_dummy_name;
 
 	return priv->soc->pins[selector].name;