drm/amd/display: Add DML path for FAMS methods

[Why]
DML needs a path for FAMS methods.

[How]
Apply instance of fams2_stream_sub_params_v2 structure with
a FAMS placeholder for DML.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Oleh Kuzhylnyi <okuzhyln@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>