msm: mdss: Fix synchronization issue for dual dsi dynamic fps

Add additional checks in dual dsi with dynamic fps(dfps) enabled.
This change fixes synchronization issues during mismatch of dfps
settings between the dsi controllers.

Change-Id: Ib98b779bec15b5b60cbba337724a0b1d093bda46
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>