msm: camera: face detect: fix stream off sync issue

Stream off will block until the active buffer
in processing queue is completed. There was small
time window where the active buffer was removed from device
queue but still was not completed.

Change-Id: Icb90053761de200a63ec7c72a2b3446582a240d7
Signed-off-by: Gjorgji Rosikopulos <grosik@codeaurora.org>