msm: mdss: fix vsync control synchronization issue

Fix the race condition when user vsync control thread turns on/off
the vsync interrupt, while frame thread updates at the same time.

Change-Id: I4e9f6df2a58702a5b2db62a7fd989e51503825aa
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>
6 files changed