leds: trigger: Add led_mc_trigger_event() function

Add a new led_mc_trigger_event() function for triggers which want to
change the color of a multi-color LED based on their trigger conditions.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240531114124.45346-6-hdegoede@redhat.com


Signed-off-by: Lee Jones <lee@kernel.org>