disp: msm: dsi: Fix DFPS sequence when constant fps is enabled

When DFPS and dynamic clock switch with constant fps are
enabled, wait for dynamic refresh done only if clock switch
is triggered. In case where only fps changes, clock remains
same. So, wait for dynamic refresh done is not required.

Change-Id: I1a96d8d6756086afe2cd6e5bdc19be27c2ffed92
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>