selftests/bpf: Switch fexit_stress to bpf_link_create() API

Use bpf_link_create() API in fexit_stress test to attach FEXIT programs.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Kui-Feng Lee <kuifeng@fb.com>
Link: https://lore.kernel.org/bpf/20220421033945.3602803-4-andrii@kernel.org

tools/testing/selftests/bpf/prog_tests/fexit_stress.c

@@ -53,7 +53,7 @@ void test_fexit_stress(void)
 					    &trace_opts);
 		if (!ASSERT_GE(fexit_fd[i], 0, "fexit load"))
 			goto out;
-		link_fd[i] = bpf_raw_tracepoint_open(NULL, fexit_fd[i]);
+		link_fd[i] = bpf_link_create(fexit_fd[i], 0, BPF_TRACE_FEXIT, NULL);
 		if (!ASSERT_GE(link_fd[i], 0, "fexit attach"))
 			goto out;
 	}