power: supply: Add a driver for Injoinic power bank ICs

This driver supports several chip variants which all share the same I2C
register interface. Since the chip will turn off and become inaccessible
under conditions outside of software control (e.g. upon button press or
input voltage removal), some special handling is needed to delay the
initialization of the IC until it is accessible.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>