selftests/bpf: Fix attach tests retcode checks

Switching to libbpf 1.0 API broke test_sock and test_sysctl as they
check for return of bpf_prog_attach to be exactly -1. Switch the check
to '< 0' instead.

Fixes: b858ba8c52b6 ("selftests/bpf: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK")
Signed-off-by: Artem Savkov <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Reviewed-by: Yafang Shao <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/test_sock.c

···
 			goto err;
 	}
 
-	if (attach_sock_prog(cgfd, progfd, test->attach_type) == -1) {
+	if (attach_sock_prog(cgfd, progfd, test->attach_type) < 0) {
 		if (test->result == ATTACH_REJECT)
 			goto out;
 		else

tools/testing/selftests/bpf/test_sysctl.c

···
 			goto err;
 	}
 
-	if (bpf_prog_attach(progfd, cgfd, atype, BPF_F_ALLOW_OVERRIDE) == -1) {
+	if (bpf_prog_attach(progfd, cgfd, atype, BPF_F_ALLOW_OVERRIDE) < 0) {
 		if (test->result == ATTACH_REJECT)
 			goto out;
 		else