msm: mdss: fix race condition with overlay off in doze mode

When stop is called for doze mode, there is a
race condition between the stop thread and the
retire signal work queue. Fix race condition by
making sure that driver waits for the retire fence
before calling the stop.

Change-Id: Icd9d5b14e4138e747f9483458da7ddb89f515c03
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>