leds: core: Add more colors from DT bindings to led_colors

The colors are already part of DT bindings. Make sure the kernel is
able to convert them to strings.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
Link: https://lore.kernel.org/r/20231008144014.1180334-1-megi@xff.cz


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