arm/dt: 8974: enable device for RGB Leds

RGB Led device must be enabled in dtsi file, since
it is supported on 8974 platform.

Also, move LEDs which are suported on all platforms to
msm8974-leds.dtsi, and move WLED changes to appropriate
dtsi files for platforms which they are supported on.

Change-Id: I5fab5a628b79751669dc0535541a0b26080427f2
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>