disp: msm: dp: fix potential delay to start authentication

Start authentication as soon as the stream is successfully powered
on and before the audio notification is sent. This will avoid a
potential delay in starting authentication if the audio subsystem
does not respond to the audio notification.

Change-Id: I83e5746ff521cfe8641f6e2bffd1bed953329a69
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>