ARM: dts: sun8i: a711: Add regulator support

The TBS A711 is using an AXP813 PMIC. Let's add all the regulators for that
board, and migrate the current, dumb, regulators to the actual ones.

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