ARM: dts: msm: disable dynamic FPS feature for SDM845

Switching refresh rate is handled as modeset in DRM framework
which tries to reprogram some of the initialization sequence in
display pipeline driving the hardware to bad state. This
change disables the feature temporarily in SDM845 until the
sequence is fixed.

Change-Id: I7b61b64bf20f8c127dae1f3ec6ff04a9c84f04c2
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>