arm64: allwinner: a64: enable AXP803 for Banana Pi M64

Banana Pi M64 board uses an AXP803 PMIC.

Enable the PMIC and its regulators.

As we have now proper regulators support, missing or dummy regulators
are changed to the correct ones.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>