drm/msm/dp: turn off audio before dp lane status toggling

There is an audio turn off timeout error whenever DP handles
the link state toggling requests from sink during audio
playback session. The audio hw is waiting for DMA write done
interrupts before issuing a audio session tear down. As the
DP controller is put into reset before link training, the
DMA write done is not sent by the DP controller hence causing
audio timeout errors. These changes turn off audio before the
DP controller is put into reset so that the audio session
tear down takes place within the stipulated time.

Change-Id: I7b88d0385a84f308d8537c2766e6fbc25a2ddc3b
Signed-off-by: Sankeerth Billakanti <sbillaka@codeaurora.org>