drm/amdgpu/dm/mst: Fix uninitialized var in pre_compute_mst_dsc_configs_for_state()

Coverity noticed this one, so let's fix it.

Fixes: ba891436 ("drm/amdgpu/mst: Stop ignoring error codes and deadlocking")
Signed-off-by: NLyude Paul <lyude@redhat.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org # v5.6+

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

@@ -1180,7 +1180,7 @@ static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
 	struct amdgpu_dm_connector *aconnector;
 	struct drm_dp_mst_topology_mgr *mst_mgr;
 	int link_vars_start_index = 0;
-	int ret;
+	int ret = 0;
 
 	for (i = 0; i < dc_state->stream_count; i++)
 		computed_streams[i] = false;