dt-bindings: leds: Add DT bindings for QTI TRI_LED driver

QTI TRI_LED driver helps configuring the output of LED channels
in TRI_LED and HR_LED peripherals. Add device tree bindings for it.

This snapshot is taken as of msm-4.14
commit 9bb584ae3a9d ("msm/sde/rotator: Add rev checks for sdmmagpie").

Change-Id: I9a4eddbf58cdb99a2f011222d58df426cd920b52
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>