drm/msm/dp: add widebus support for sst and mst modes

Implement widebus support for all dp use-cases as per the
hardware design recommendations. Widebus reduces the dp
pclk by half and doubles the sw_m and sw_n values to correct
the stream configuration data.

CRs-Fixed: 2325207
Change-Id: Ieb2e4a21bc82ab73563a4fd2edb68e59dda29069
Signed-off-by: Govinda Rajulu Chenna <gchenna@codeaurora.org>