selftests: bpf: Pass program to bpf_prog_detach in flow_dissector

Calling bpf_prog_detach is incorrect, since it takes target_fd as
its argument. The intention here is to pass it as attach_bpf_fd,
so use bpf_prog_detach2 and pass zero for target_fd.

Fixes: 06716e04 ("selftests/bpf: Extend test_flow_dissector to cover link creation")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200629095630.7933-7-lmb@cloudflare.com

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

@@ -527,8 +527,8 @@ static void test_skb_less_prog_attach(struct bpf_flow *skel, int tap_fd)
 
 	run_tests_skb_less(tap_fd, skel->maps.last_dissection);
 
-	err = bpf_prog_detach(prog_fd, BPF_FLOW_DISSECTOR);
-	CHECK(err, "bpf_prog_detach", "err %d errno %d\n", err, errno);
+	err = bpf_prog_detach2(prog_fd, 0, BPF_FLOW_DISSECTOR);
+	CHECK(err, "bpf_prog_detach2", "err %d errno %d\n", err, errno);
 }
 
 static void test_skb_less_link_create(struct bpf_flow *skel, int tap_fd)