leds: leds-qti-tri-led: Add LED driver for QTI TRI_LED module

QTI TRI_LED module has 3 current sinks at max for LED driver and
each is controlled by a PWM channel used for LED dimming or blinking.
Add the driver to support it.

Change-Id: Icac3ad7d18f13871c94e58156775267ed0c60fd9
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>