net: dsa: mv88e6xxx: add phylink_get_caps for the mv88e6320/21 family

As of commit de5c9bf4 ("net: phylink: require supported_interfaces to
be filled")
Marvell 88e6320/21 switches fail to be probed:

...
mv88e6085 30be0000.ethernet-1:00: phylink: error: empty supported_interfaces
error creating PHYLINK: -22
...

The problem stems from the use of mv88e6185_phylink_get_caps() to get
the device capabilities.
Since there are serdes only ports 0/1 included, create a new dedicated
phylink_get_caps for the 6320 and 6321 to properly support their
set of capabilities.

Fixes: de5c9bf4 ("net: phylink: require supported_interfaces to be filled")
Signed-off-by: Steffen Bätz <steffen@innosonix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20240508072944.54880-2-steffen@innosonix.deSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -697,6 +697,18 @@ static void mv88e6352_phylink_get_caps(struct mv88e6xxx_chip *chip, int port,
 	}
 }
 
+static void mv88e632x_phylink_get_caps(struct mv88e6xxx_chip *chip, int port,
+				       struct phylink_config *config)
+{
+	unsigned long *supported = config->supported_interfaces;
+
+	/* Translate the default cmode */
+	mv88e6xxx_translate_cmode(chip->ports[port].cmode, supported);
+
+	config->mac_capabilities = MAC_SYM_PAUSE | MAC_10 | MAC_100 |
+				   MAC_1000FD;
+}
+
 static void mv88e6341_phylink_get_caps(struct mv88e6xxx_chip *chip, int port,
 				       struct phylink_config *config)
 {
@@ -5093,7 +5105,7 @@ static const struct mv88e6xxx_ops mv88e6320_ops = {
 	.gpio_ops = &mv88e6352_gpio_ops,
 	.avb_ops = &mv88e6352_avb_ops,
 	.ptp_ops = &mv88e6352_ptp_ops,
-	.phylink_get_caps = mv88e6185_phylink_get_caps,
+	.phylink_get_caps = mv88e632x_phylink_get_caps,
 };
 
 static const struct mv88e6xxx_ops mv88e6321_ops = {
@@ -5139,7 +5151,7 @@ static const struct mv88e6xxx_ops mv88e6321_ops = {
 	.gpio_ops = &mv88e6352_gpio_ops,
 	.avb_ops = &mv88e6352_avb_ops,
 	.ptp_ops = &mv88e6352_ptp_ops,
-	.phylink_get_caps = mv88e6185_phylink_get_caps,
+	.phylink_get_caps = mv88e632x_phylink_get_caps,
 };
 
 static const struct mv88e6xxx_ops mv88e6341_ops = {