power: supply: add cros-ec USBPD charger driver.

This driver gets various bits of information about what is connected to
USB PD ports from the EC and converts that into power_supply properties.

Signed-off-by: Sameer Nanda <snanda@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>