ramips: mt7620: enable autonegotiation for all ports

This enables autonegotiation for all ephy ports on probe.
Some devices do not configure the ports, particularly port 4.

Signed-off-by: Gaspare Bruno <gaspare@anlix.io>
[replace magic values ; reword commit message]
Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/ramips/files/drivers/net/ethernet/ralink/gsw_mt7620.c

@@ -171,6 +171,7 @@ static void mt7620_hw_init(struct mt7620_gsw *gsw, int mdio_mode)
 		for (i = 0; i <= 4; i++) {
 			val = _mt7620_mii_read(gsw, gsw->ephy_base + i, MII_BMCR);
 			val &= ~BMCR_PDOWN;
+			val |= BMCR_ANRESTART | BMCR_ANENABLE | BMCR_SPEED100;
 			_mt7620_mii_write(gsw, gsw->ephy_base + i, MII_BMCR, val);
 		}
 	}