power: supply: add ChromeOS EC based charge control driver

The ChromeOS Embedded Controller implements a command to control charge
thresholds and behaviour.

Use it to implement the standard Linux charge_control_start_threshold,
charge_control_end_threshold and charge_behaviour sysfs UAPIs.

The driver is designed to be probed via the cros_ec mfd device.

Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20240630-cros_ec-charge-control-v5-4-8f649d018c52@weissschuh.net


Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>