drm/amd/display: Call dc_stream_release for remove link enc assignment

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Call dc_stream_release for remove link enc assignment [Why] A porting error resulted in the stream assignment for the link being retained without being released - a memory leak. [How] Fix the porting error by adding back the dc_stream_release() intended as part of the original patch.