net: sparx5: skip low-speed configuration when port is RGMII

When doing a port config, we configure low-speed port devices, among
other things. We have a check to ensure, that the device is indeed a
low-speed device, an not a high-speed device. Add an additional check,
to ensure that the device is not an RGMII device.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Tested-by: Robert Marko <robert.marko@sartura.hr>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20241220-sparx5-lan969x-switch-driver-4-v5-4-fa8ba5dff732@microchip.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>