net: dsa: mt7530: explain exposing MDIO bus of MT7531AE better

Unlike MT7531BE, the GPIO 6-12 pins are not used for RGMII on MT7531AE.
Therefore, the GPIO 11-12 pins are set to function as MDC and MDIO to
expose the MDIO bus of the switch. Replace the comment with a better
explanation.
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mt7530.c

@@ -2635,7 +2635,10 @@ mt7531_setup(struct dsa_switch *ds)
 	if (!priv->p5_sgmii) {
 		mt7531_pll_setup(priv);
 	} else {
-		/* Let ds->user_mii_bus be able to access external phy. */
+		/* Unlike MT7531BE, the GPIO 6-12 pins are not used for RGMII on
+		 * MT7531AE. Set the GPIO 11-12 pins to function as MDC and MDIO
+		 * to expose the MDIO bus of the switch.
+		 */
 		mt7530_rmw(priv, MT7531_GPIO_MODE1, MT7531_GPIO11_RG_RXD2_MASK,
 			   MT7531_EXT_P_MDC_11);
 		mt7530_rmw(priv, MT7531_GPIO_MODE1, MT7531_GPIO12_RG_RXD3_MASK,