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

Moreover, the AXP20X can also expose the current current and voltage
values of the AC power supply.

This adds the driver which exposes the status of the AC power supply of
the AXP20X and AXP22X PMICs.
Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
[removed unused elements from struct axp20x_ac_power]
Signed-off-by: Sebastian Reichel <sre@kernel.org>