disp: msm: dp: link training enhancements

Update the link training process along with the AUX
communications during link training as per hardware
recommendations.

Update the pre-emphasis and swing values for active
lanes only instead of all lanes.

During link training, update pre-emphasis and swing
values in hardware first and then update sink.

CRs-Fixed: 2458753
Change-Id: Ie05c9d6508b0c564b194032ae4ebb1bc5550e7b8
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>