drm/msm/dp: exit super speed mode when sink doesn't support it

Parse the DisplayPort Capability Data (DPCD) to get the number of
lanes  supported by the sink. If sink doesn't support super speed
USB concurrency for which sink amy request 2 lanes, request USB
driver to exit the super speed mode so that DisplayPort driver can
use all the lanes for data.

CRs-Fixed: 2093361
Change-Id: I076d14f4d04165dab8d8ca130ce59cb79acac6b9
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>