power: supply: add charge_behaviour attributes

This a revised version of
"[RFC] add standardized attributes for force_discharge and inhibit_charge" [0],
incorporating discussion results.

The biggest change is the switch from two boolean attributes to a single
enum attribute.

[0] https://lore.kernel.org/platform-driver-x86/21569a89-8303-8573-05fb-c2fec29983d1@gmail.com/



Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20211123232704.25394-2-linux@weissschuh.net


Signed-off-by: Hans de Goede <hdegoede@redhat.com>