drm/amd/display: query hdcp capability during link detect

[Why]
Query the hdcp caps of a link, it is useful and can be reported to the user

[How]
Create a query function and call it during link detect

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>