drm/msm/dp: fix audio notification path for boot up use case

Fix the audio notification path by triggering the sending of
the notification once the audio codec has been registered. This
allows the main display thread to execute until completion,
and for the audio setup to be done asynchronously once the audio
subsystem is ready.

CRs-Fixed: 2118984
Change-Id: Ib0712f983ac86f224fae66ca8ef2a07e3ae76ac2
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>