ipq40xx: convert Orbi led labels to function/color

ipq40xx: convert Orbi led labels to function/color

The eight leds controlled by the LED controller are RGB leds themselves
but are flashing white by default. The color part is controlled by GPIOs
53 (green), 54 (red), 57 (blue) and 60 (white).
Therefore define the led nodes of the controller as white instead of RBG
as well as backlight as their function.

Signed-off-by: Christoph Krapp <achterin@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/20877
Signed-off-by: Robert Marko <robimarko@gmail.com>