net: dsa: b53: do not enable RGMII delay on bcm63xx

bcm63xx's RGMII ports are always in MAC mode, never in PHY mode, so we
shouldn't enable any delays and let the PHY handle any delays as
necessary.

This fixes using RGMII ports with normal PHYs like BCM54612E, which will
handle the delay in the PHY.

Fixes: ce3bf948 ("net: dsa: b53: add support for BCM63xx RGMIIs")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250602193953.1010487-3-jonas.gorski@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>