arm64: allwinner: a64: add Ethernet PHY regulator for several boards

On several A64 boards the Ethernet PHY is powered by the DC1SW regulator
on the AXP803 PMIC.

Add phy-handle property to these boards' emac node.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Tested-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>