ARM: dts: sunxi: Add dtsi for AXP22x PMIC

The AXP22x family of PMIC is used with some Allwinner SoCs. This
includes the AXP221, AXP221s and AXP223. They differ in the host
interface, maximum supply current for DCDC1 regulator, and default
voltage and state for various LDO regulators. Also, the AXP221s
does not support fine calibration of the battery fuel gauge.

This patch adds a dtsi file for all the common bindings for these
PMICs. Currently this is just listing all the regulator nodes. The
regulators are initialized based on their device node names.

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