drm/amd/display: move edp sink present detection to hw init

[Why]
At SW init, we may not be ready to do detect eDP sink.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>