sunxi: Enable EMAC on the Bananapi M3

The Bananapi M3 has an RTL8211E PHY connected to the EMAC using
RGMII. The PHY is powered by DCDC1 through SW @ 3.3V.

The board is designed to use 3.3V with RGMII, instead of the standard
reduced voltage of 2.5V we see everywhere. DLDO3, which provides the
I/O voltages, is raised to match.

This patch enables the EMAC and Realtek PHY drivers in the defconfig.
The device tree file already has the EMAC enabled.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>