Now that we support link-state-change interrupts, wire up MT7531 IRQ
line which is connected to GPIO#53 according to the schematics [1].
As a result, PHY state no longer needs to be polled on that board.
[1]: https://forum.banana-pi.org/t/bpi-r64-mt7622-schematic-diagram-public/10118
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
