drm/msm/sde: avoid lock while dumping fence status

while crtc_commit is in progress last_close can be triggered
which accquires mode config locks, hence avoid using lock while
dumping the fence status on connector when lock is already taken.

Change-Id: I4e2032a65b3483dd276a2c82f339016fc2f3a93f
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>