arm64: allwinner: orangepi-pc2: Enable dwmac-sun8i

The dwmac-sun8i hardware is present on the Orange PI PC2.
It uses an external PHY rtl8211e via RGMII.

This patch create the needed regulator, emac and phy nodes.
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>