ARM: dts: msm: update LPG/LED configuration in PM855L

Add ramp configurations for the LPG channels so that the RGB LEDs
connecting to these channels can be controlled with blinking patterns.
Also add timer as the default trigger for RGB LEDs.

Change-Id: I7a416a724cfca177b1ab16546ffa197e56f70e26
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>