drm/amd/display: prevent seamless boot on displays that don't have the preferred dig

Seamless boot requires VBIOS to select dig matching to link order wise. A significant
amount of dal logic makes assumption we are using preferred dig for eDP and if this
isn't the case then seamless boot is not supported.

Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>