arm: rmobile: rzg2_beacon: Enable proper Ethernet PHY

The wrong phy was being enabled, because it worked and the proper
PHY did not.  After the Renesas maintainer made some adjustments
to the device tree, Linux was able to use the proper driver, and
when that device tree was ported to Linux, the ethernet stopped
working due to the lack of rgmii-rxid support.  Now that
rgmii-rxid is supported, enable the proper driver to restore
ethernet function.

Fixes: 1eaf61c8 ("arm: dts: beacon-rzg2: Resync device trees with Linux 5.16-rc3")
Signed-off-by: Adam Ford <aford173@gmail.com>