ramips: add wan2 support for MQmaker WiTi

ramips: add wan2 support for MQmaker WiTi

The PHY of the wan2 port on MQmaker WiTi is wired to the second MAC of the
SoC. Rename the wan interface to wan1 and define it under the switch node,
effectively disabling the PHY muxing of the MT7530 switch's phy4.

Define the PHY of the wan2 port and adjust the gmac1 node accordingly. Now
that the PHY muxing feature is not being used anymore, the wan2 port can be
used to achieve 2 Gbps total bandwidth to the CPU.

Tested-by: Demetris Ierokipides <ierokipides.dem@gmail.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>