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.

Fixes: 0bb24555 ("drm/amd/display: retain/release at proper places in link_enc assignment")
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c

@@ -122,6 +122,7 @@ static void remove_link_enc_assignment(
 				stream->link_enc = NULL;
 				state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[i].eng_id = ENGINE_ID_UNKNOWN;
 				state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[i].stream = NULL;
+				dc_stream_release(stream);
 				break;
 			}
 		}