ARM: dts: msm: add rgb led node for PMI8994

PMI8994 RGB module provides support for notification
leds - red, green, and blue. These leds are operated
via pwm channels.

Change-Id: I23eaa45fb0d0583b57ddf40352dbf8cdbfce9401
Signed-off-by: Mohan Pallaka <mpallaka@codeaurora.org>