disp: msm: dsi: defer clk setting when doing const_fps RFI

When doing const fps RFI, dynamic refresh clock was done
in the next frame kick off, so as the orginal RFI work flow,
the clock setting also should be done here.

Change-Id: Ic3e6a35dc7264df028f5d848ac6f1eea04a95126
Signed-off-by: Yuan Zhao <yzhao@codeaurora.org>