net: dsa: mt7530: do not run mt7530_setup_port5() if port 5 is disabled

There's no need to run all the code on mt7530_setup_port5() if port 5 is
disabled. The only case for calling mt7530_setup_port5() from
mt7530_setup() is when PHY muxing is enabled. That is because port 5 is not
defined as a port on the devicetree, therefore, it cannot be controlled by
phylink.

Because of this, run mt7530_setup_port5() if priv->p5_intf_sel is
P5_INTF_SEL_PHY_P0 or P5_INTF_SEL_PHY_P4. Remove the P5_DISABLED case from
mt7530_setup_port5().

Stop initialising the interface variable as the remaining cases will always
call mt7530_setup_port5() with it initialised.
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20240122-for-netnext-mt7530-improvements-1-v3-7-042401f2b279@arinc9.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mt7530.c

@@ -942,9 +942,6 @@ static void mt7530_setup_port5(struct dsa_switch *ds, phy_interface_t interface)
 		/* MT7530_P5_MODE_GMAC: P5 -> External phy or 2nd GMAC */
 		val &= ~MHWTRAP_P5_DIS;
 		break;
-	case P5_DISABLED:
-		interface = PHY_INTERFACE_MODE_NA;
-		break;
 	default:
 		dev_err(ds->dev, "Unsupported p5_intf_sel %d\n",
 			priv->p5_intf_sel);
@@ -2331,8 +2328,6 @@ mt7530_setup(struct dsa_switch *ds)
 		 * Set priv->p5_intf_sel to the appropriate value if PHY muxing
 		 * is detected.
 		 */
-		interface = PHY_INTERFACE_MODE_NA;
-
 		for_each_child_of_node(dn, mac_np) {
 			if (!of_device_is_compatible(mac_np,
 						     "mediatek,eth-mac"))
@@ -2364,6 +2359,8 @@ mt7530_setup(struct dsa_switch *ds)
 			break;
 		}
 
+		if (priv->p5_intf_sel == P5_INTF_SEL_PHY_P0 ||
+		    priv->p5_intf_sel == P5_INTF_SEL_PHY_P4)
 			mt7530_setup_port5(ds, interface);
 	}