leds: Add driver for LEDs from qnap-mcu devices

This adds a driver that connects to the qnap-mcu mfd driver and provides
access to the LEDs on it.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20241107114712.538976-6-heiko@sntech.de


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