drm/msm/mdp5: Fix wait-for-commit for cmd panels

stable inclusion
from stable-5.10.20
commit 5c49fc7b5d9b3aabf5e5bfb4fe96bbd3cc11e63f
bugzilla: 50608

--------------------------------

[ Upstream commit 68e4f01f ]

Before the offending commit in msm_atomic_commit_tail wait_flush was
called once per frame, after the commit was submitted. After it
wait_flush is also called at the beginning to ensure previous
potentially async commits are done.

For cmd panels the source of wait_flush is a ping-pong irq notifying
a completion. The completion needs to be notified with complete_all so
multiple waiting parties (new async committers) can proceed.

Signed-off-by: Iskren Chernev <iskren.chernev@gmail.com>
Suggested-by: Rob Clark <robdclark@gmail.com>
Fixes: 2d99ced7 ("drm/msm: async commit support")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>