ARM: dts: msm: Add WLED module for PMI thorium

Add WLED module for PMI thorium.
WLED module drives a series / parallel combination of string(s)
of white LEDs that are used to backlight LCD panels.

Change-Id: I26afafdce43e185d759718f70b3c191698edac52
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>