drm/amd/display: Fix ineffective setting of max bpc property

[Why]
Regression was introduced where setting max bpc property has no effect
on the atomic check and final commit. It has the same effect as max bpc
being stuck at 8.

[How]
Correctly propagate max bpc with the new connector state.
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -5049,7 +5049,8 @@ create_validate_stream_for_sink(struct amdgpu_dm_connector *aconnector,
 	struct drm_connector *connector = &aconnector->base;
 	struct amdgpu_device *adev = connector->dev->dev_private;
 	struct dc_stream_state *stream;
-	int requested_bpc = connector->state ? connector->state->max_requested_bpc : 8;
+	const struct drm_connector_state *drm_state = dm_state ? &dm_state->base : NULL;
+	int requested_bpc = drm_state ? drm_state->max_requested_bpc : 8;
 	enum dc_status dc_result = DC_OK;
 
 	do {