mfd: axp20x: Add AXP22x PMIC support

mfd: axp20x: Add AXP22x PMIC support

Add support for the AXP22x PMIC devices to the existing AXP20x driver.
This includes the AXP221 and AXP223, which are identical except for
the external data bus. Only AXP221 is added for now. AXP223 will be
added after it's Reduced Serial Bus (RSB) interface is supported.

AXP22x defines a new set of registers, power supplies and regulators,
but most of the API is similar to the AXP20x ones.

A new irq chip definition is used, even though the available interrupts
on AXP22x is a subset of those on AXP20x. This is done so the interrupt
numbers match those on the datasheet.

This patch only enables the interrupts, system power-off function, and PEK
sub-device. The regulator driver must first support different variants
before we enable it from the mfd driver.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
[wens@csie.org: fix interrupts and move regulators to separate patch]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>