power: supply: core: introduce power_supply_for_each_psy()

power: supply: core: introduce power_supply_for_each_psy()

All existing callers of power_supply_for_each_device() want to iterate
over 'struct power_supply', not 'struct device'.
The power_supply_for_each_device() forces each caller to duplicate the
logic to go from one to the other.
Introduce power_supply_for_each_psy() to simplify the callers.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20241210-power-supply-dev_to_psy-v2-2-9d8c9d24cfe4@weissschuh.net
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>