ARM: dts: msm: enable ulps feature for sdm670 platform

Enable ulps feature for all the panels on sdm670 platform,
which support this feature. This is needed to achieve extra
power savings during static display use case.

Change-Id: I2ef41aae135dfb4ccee9c16f03c250eb0b65a376
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>