ARM: dts: sun8i: q8-common: Add AXP223 PMIC device and regulator nodes

A23/A33 Q8 tablets have an X-Powers AXP223 PMIC connected via RSB. Its
regulators provide power to various parts of the SoC and the board.

Also add lcd regulator supply for simplefb and update the existing
vmmc-supply for mmc0.

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