drm/amd/display: Refactor dp vendor parsing logic to a function

Refactor dp vendor parsing int to a new function, and call it before
get_active_converter_info().

Also, add a flag to skip parsing of Display ID 2.0. Some devices fail on
readind DID2, but we shouldn't fail EDID read because of it. Add this
flag to facilitate the logic.

Signed-off-by: John Barberiz <John.Barberiz@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>