power: supply: leds: Add power_supply_[un]register_led_trigger()

power: supply: leds: Add power_supply_[un]register_led_trigger()

Add power_supply_[un]register_led_trigger() helper functions.

The primary goal of this is as a preparation patch for adding an activate
callback to the power-supply LED triggers to ensure that power-supply
LEDs get the correct initial value when the LED gets registered after
the power_supply has been registered (this will use the psy back pointer).

There also is quite a lot of code duplication in the existing LED trigger
registration in the form of the kasprintf() for the name-template for each
trigger + related error handling. This duplication is removed by these
new helpers.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240531134702.166145-2-hdegoede@redhat.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>