msm: mdss: Correct AD state in driver

There is one recent change in MDP driver that removes the vsync handler
when device goes to suspend, and this change puts AD into an incorrect
state after suspend/resume. This change modify the AD implementation
to coordinate the MDP driver change mentioned above by adding the AD
vsync back during resume. This change also fix the state resetting
during AD off case.

Change-Id: Ic31a791fa6f8fe5ba731837f8d9808d20e2d31e6
Signed-off-by: Ping Li <pingli@codeaurora.org>