selftests/bpf: properly return error from bpf_flow_load

Right now we incorrectly return 'ret' which is always zero at that
point.
Signed-off-by: NStanislav Fomichev <sdf@google.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/flow_dissector_load.h

@@ -25,19 +25,19 @@ static inline int bpf_flow_load(struct bpf_object **obj,
 
 	main_prog = bpf_object__find_program_by_title(*obj, section_name);
 	if (!main_prog)
-		return ret;
+		return -1;
 
 	*prog_fd = bpf_program__fd(main_prog);
 	if (*prog_fd < 0)
-		return ret;
+		return -1;
 
 	prog_array = bpf_object__find_map_by_name(*obj, map_name);
 	if (!prog_array)
-		return ret;
+		return -1;
 
 	prog_array_fd = bpf_map__fd(prog_array);
 	if (prog_array_fd < 0)
-		return ret;
+		return -1;
 
 	if (keys_map_name && keys_fd) {
 		keys = bpf_object__find_map_by_name(*obj, keys_map_name);