bpf: selftests: Add non function pointer test to struct_ops

This patch adds a "void *owner" member.  The existing
bpf_tcp_ca test will ensure the bpf_cubic.o and bpf_dctcp.o
can be loaded.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210212021037.267278-1-kafai@fb.com

tools/testing/selftests/bpf/bpf_tcp_helpers.h

@@ -177,6 +177,7 @@ struct tcp_congestion_ops {
 	 * after all the ca_state processing. (optional)
 	 */
 	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
+	void *owner;
 };
 
 #define min(a, b) ((a) < (b) ? (a) : (b))