Revert "drm/msm/dp: optimize link rate selection"

This reverts commit 6b837d21.

This changes allows the DisplayPort driver to configure the
link using the maximum capabilities of the sink.

Change-Id: I4084dd7c9d3be22d4d5650139b09ff459668e39c
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>