drm/msm/sde: Fix suspend-resume issue after switching dsi clk

Fixes suspend-resume not working after switching dsi clk for
video mode. While switching the dsi clk, FLAG_SEAMLESS_DYN_CLK
is set leading to enable dsi clks which causes extra refcount.
Add check for command mode.

Change-Id: I814eb9c87daf387b5d57c5a3dddf7ae1e60fe784
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>