ARM: dts: msm: Remove the led triggers for DTP8996

The RGB leds are controlled in userspace via display HAL,
remove the default triggers to make sure the kernel driver
won't control them to cause the mess.

Change-Id: I495dacab3b6bc14158d480e1779199e6f5747b61
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>