power: supply: cros_charge-control: add mutex for driver data

Concurrent accesses through sysfs may lead to inconsistent state in the
priv data. Introduce a mutex to avoid this.

Fixes: c6ed48ef ("power: supply: add ChromeOS EC based charge control driver")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20241208-cros_charge-control-v2-v1-1-8d168d0f08a3@weissschuh.net


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>