net: stmmac: enable EEE in MII, GMII or RGMII only

Note in the databook - Section 4.4 - EEE :
" The EEE feature is not supported when the MAC is configured to use the
TBI, RTBI, SMII, RMII or SGMII single PHY interface. Even if the MAC
supports multiple PHY interfaces, you should activate the EEE mode only
when the MAC is operating with GMII, MII, or RGMII interface."

Applying this restriction solves a stability issue observed on Amlogic
gxl platforms operating with RMII interface and the internal PHY.

Fixes: 83bf79b6 ("stmmac: disable at run-time the EEE if not supported")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Tested-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -364,9 +364,15 @@ static void stmmac_eee_ctrl_timer(struct timer_list *t)
 bool stmmac_eee_init(struct stmmac_priv *priv)
 {
 	struct net_device *ndev = priv->dev;
+	int interface = priv->plat->interface;
 	unsigned long flags;
 	bool ret = false;
 
+	if ((interface != PHY_INTERFACE_MODE_MII) &&
+	    (interface != PHY_INTERFACE_MODE_GMII) &&
+	    !phy_interface_mode_is_rgmii(interface))
+		goto out;
+
 	/* Using PCS we cannot dial with the phy registers at this stage
 	 * so we do not support extra feature like EEE.
 	 */