msm: fbdev: dp: send video notiification after audio teardown

DP audio teardown is received from the AFE audio codec. Wait for
audio_comp flag before calling the video notification function.
This ensures that the DP audio engine is in the disabled (MUTE)
state, before disabling the video.

Change-Id: Id0f9d67a2364ac0987841f148042d90acb4f6db0
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>