drm/amd/display: implement force function in amdgpu_dm_connector_funcs

[Why]
When userspace (IGT) inserts EDID with audio data (ELD), EDID
is not updated.

[How]
Implements force function (amdgpu_dm_connector_funcs_force) in
amdgpu_dm_connector_funcs to create emulated sink and to handle
EDID.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Wenchieh Chien <wenchieh.chien@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>