ARM: dts: msm: add reg bus scale properties for msmtitanium/8937

Add MDSS reg bus scale properties for msm8937 and msmtitanium.
These votes are required for faster reg access especially in cases
like histogram/gamut where we read large number of registers.

Change-Id: I42ed99234eddfcf21e962a3266b8905a38fccbac
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>