ARM: dts: msm: Specify display refresh rates for Truly 720p panel

Specify the minimum and maximum refresh rate for the Truly 720p
video mode panel used in msm8917 CDP and MTP. This settings are
added to achieve the dynamic fps functionality.

Change-Id: Iec26e72ef27c25522f2f93a3f320e7bf909e23fd
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>