ARM: dts: sun8i: r40: bananapi-m2-ultra: Enable GMAC ethernet controller

The Bananapi M2 Ultra has a Realtek RTL8211E RGMII PHY tied to the GMAC.
The PMIC's DC1SW output provides power for the PHY, while the ALDO2
output provides I/O voltages on both sides.

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>