drm/amd/display: Attach privacy screen to DRM connector

[WHY]
If a system has a privacy screen advertised by a driver it should
be included in the DRM connector for the eDP panel.

[HOW]
Detect statically declared privacy screens when creating eDP connector
and attach privacy screen DRM properties.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>