msm: mdss: notify frame done for wifi display kickoff without buffer

The frame done notification is required even for kickoff without
output buffer. This happens for pan-display path, where a kickoff
can be triggered without output buffer queueing first. By notifying
the frame done event, it allows the client to release retire fence
properly.

Change-Id: Ia29acf58819641e84a58061f9c06ee74cf1bec06
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>