The X-Powers AXP20X and AXP22X PMICs expose the status of AC power
supply.

This adds the AC power supply driver to the MFD cells of the AXP22X
PMICs.
Signed-off-by: NQuentin Schulz <quentin.schulz@free-electrons.com>
Acked-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Acked-By: NSebastian Reichel <sre@kernel.org>
Acked-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>