This commit introduces LED drivers for rtl8366rb, enabling LEDs to be
described in the device tree using the same format as qca8k. Each port
can configure up to 4 LEDs.

If all LEDs in a group use the default state "keep", they will use the
default behavior after a reset. Changing the brightness of one LED,
either manually or by a trigger, will disable the default hardware
trigger and switch the entire LED group to manually controlled LEDs.
Once in this mode, there is no way to revert to hardware-controlled LEDs
(except by resetting the switch).

Software triggers function as expected with manually controlled LEDs.
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>