leds: core: Unexport led_colors[] array

There are no external users left, make the array static.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20240613-cros_ec-led-v3-3-500b50f41e0f@weissschuh.net


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