net: dsa: lantiq_gswip: Enable GSWIP_MII_CFG_EN also for internal PHYs

Enable GSWIP_MII_CFG_EN also for internal PHYs to make traffic flow.
Without this the PHY link is detected properly and ethtool statistics
for TX are increasing but there's no RX traffic coming in.

Fixes: 14fceff4 ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Suggested-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/lantiq_gswip.c

@@ -1541,9 +1541,7 @@ static void gswip_phylink_mac_link_up(struct dsa_switch *ds, int port,
 {
 	struct gswip_priv *priv = ds->priv;
 
-	/* Enable the xMII interface only for the external PHY */
-	if (interface != PHY_INTERFACE_MODE_INTERNAL)
-		gswip_mii_mask_cfg(priv, 0, GSWIP_MII_CFG_EN, port);
+	gswip_mii_mask_cfg(priv, 0, GSWIP_MII_CFG_EN, port);
 }
 
 static void gswip_get_strings(struct dsa_switch *ds, int port, u32 stringset,