drm/msm/sde: remove signaled fences from local fence list

Remove signaled fences from local fence list to avoid
accessing freed list object while moving the un-signaled
fences.

Change-Id: I4f25e0eaa51c3d62b07a4f82bc759d22c4a50209
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>