drm/amd/display: DIO Supported for virtual displays

[WHY]
Virtual displays do not use the backend of the pipe, and so have
infinite backend bandwidth.

[HOW]
Add a skip_dio_check bool to the VBA struct, which is used to override
the DIOSupport calculations.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Acked-by: Chris Park <Chris.Park@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>