tools/testing: Remove unused variable

Remove unused variable "ret2".
Signed-off-by: zuoqilin <zuoqilin@yulong.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210414141639.1446-1-zuoqilin1@163.com

tools/testing/selftests/bpf/progs/test_tunnel_kern.c

@@ -396,7 +396,7 @@ int _ip6vxlan_get_tunnel(struct __sk_buff *skb)
 SEC("geneve_set_tunnel")
 int _geneve_set_tunnel(struct __sk_buff *skb)
 {
-	int ret, ret2;
+	int ret;
 	struct bpf_tunnel_key key;
 	struct geneve_opt gopt;