drm/msm/sde: remove release fence signal from frame done

Move back the release fence signaling to complete commit
for cmd mode panels. As it is causing unbalanced prepare and
signal output fence because few prepare fence calls are not
followed by a kickoff.

Change-Id: Ib1cef5883c66306119c7f7f98af7b2b72017e1c7
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>