drm/msm: Fix wait_fence submitqueue leak

drm/msm: Fix wait_fence submitqueue leak

[ Upstream commit ea0006d390a28012f8187717aea61498b2b341e5 ]

We weren't dropping the submitqueue reference in all paths.  In
particular, when the fence has already been signalled. Split out
a helper to simplify handling this in the various different return
paths.

Fixes: a61acbbe9cf8 ("drm/msm: Track "seqno" fences by idr")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20211111192457.747899-2-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>