mlxsw: spectrum_router: Compare only trees which are in use during tree get

Only trees which are in use should be compared to requested prefix usage.

Fixes: 53342023ee ("mlxsw: spectrum_router: Implement LPM trees management")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -345,7 +345,8 @@ mlxsw_sp_lpm_tree_get(struct mlxsw_sp *mlxsw_sp,
 
 	for (i = 0; i < MLXSW_SP_LPM_TREE_COUNT; i++) {
 		lpm_tree = &mlxsw_sp->router.lpm_trees[i];
-		if (lpm_tree->proto == proto &&
+		if (lpm_tree->ref_count != 0 &&
+		    lpm_tree->proto == proto &&
 		    mlxsw_sp_prefix_usage_eq(&lpm_tree->prefix_usage,
 					     prefix_usage))
 			goto inc_ref_count;