net: dsa: b53: allow RGMII for bcm63xx RGMII ports

net: dsa: b53: allow RGMII for bcm63xx RGMII ports

[ Upstream commit 5ea0d42c1980e6d10e5cb56a78021db5bfcebaaf ]

Add RGMII to supported interfaces for BCM63xx RGMII ports so they can be
actually used in RGMII mode.

Without this, phylink will fail to configure them:

[    3.580000] b53-switch 10700000.switch GbE3 (uninitialized): validation of rgmii with support 0000000,00000000,00000000,000062ff and advertisement 0000000,00000000,00000000,000062ff failed: -EINVAL
[    3.600000] b53-switch 10700000.switch GbE3 (uninitialized): failed to connect to PHY: -EINVAL
[    3.610000] b53-switch 10700000.switch GbE3 (uninitialized): error -22 setting up PHY for tree 0, switch 0, port 4

Fixes: ce3bf94871f7 ("net: dsa: b53: add support for BCM63xx RGMIIs")
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Link: https://patch.msgid.link/20250602193953.1010487-5-jonas.gorski@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>