board: ge: bx50v3: add phy reset GPIO

board: ge: bx50v3: add phy reset GPIO

Add PHY's reset GPIO, so that U-Boot does a PHY hard reset.
This is needed, since the PHY might become unresponsive if
watchdog reboots the system while a transaction is ongoing.

The reset GPIO is added to the U-Boot specific DT files, since
the kernel does not setup the reserved registers correctly after
resetting the PHY and thus must not reset it.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>