generic: mxl-gpy: allow configuring LED registers

generic: mxl-gpy: allow configuring LED registers

Add a patch to allow modification of the PHY LED configuration. This is
required for boards, where the reset configuration of LED functions is
incompatibe with the usage of the device LEDs.

This is the case for the ASUS TUF-AX4200 Wireless router. It requires
modification of the LED configuration because as the WAN LED on the
front of the device is driven by the PHY. Without patching, it would
only illuminate in case the Link speed is 100 Mbit/s.

Signed-off-by: David Bauer <mail@david-bauer.net>