drm/amd/display: set default return value for ODM Combine debugfs

[Why&How]
Set a default return value of -ENOTSUPP to indicate that the hardware
does not support querying ODM Combine mode.
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1211,7 +1211,7 @@ static int odm_combine_segments_show(struct seq_file *m, void *unused)
 	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 	struct dc_link *link = aconnector->dc_link;
 	struct pipe_ctx *pipe_ctx = NULL;
-	int i, segments = 0;
+	int i, segments = -EOPNOTSUPP;
 
 	for (i = 0; i < MAX_PIPES; i++) {
 		pipe_ctx = &link->dc->current_state->res_ctx.pipe_ctx[i];