drm/msm/dp: fix suspend/resume audio issue

On suspend, DP is powered off which erases EDID. On resume,
DP checks for audio support from EDID which has already
been reset. Retain audio information across DP power cycles
to avoid issues like this. In case the cable is removed and
connected again, EDID is read again and audio status is updated.

Change-Id: I82e84dee67507e825f4b4134db6d1e779d0324ce
CRs-Fixed: 2325990
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>
Signed-off-by: Abhijith Desai <desaia@codeaurora.org>