power-supply: Propagate error returned by power_supply_find_supply_from_node()

Callers of power_supply_find_supply_from_node(), i.e.
power_supply_check_supplies(), must propagate the errors returned by it instead
of returning their own.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>