selftests/bpf: Fix compilation failure when CONFIG_NET_FOU!=y

Without CONFIG_NET_FOU bpf selftests are unable to build because of
missing definitions. Add ___local versions of struct bpf_fou_encap and
enum bpf_fou_encap_type to fix the issue.

Signed-off-by: Artem Savkov <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
  */
 #define ASSIGNED_ADDR_VETH1 0xac1001c8
 
+struct bpf_fou_encap___local {
+	__be16 sport;
+	__be16 dport;
+} __attribute__((preserve_access_index));
+
+enum bpf_fou_encap_type___local {
+	FOU_BPF_ENCAP_FOU___local,
+	FOU_BPF_ENCAP_GUE___local,
+};
+
+struct bpf_fou_encap;
+
 int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
 			  struct bpf_fou_encap *encap, int type) __ksym;
 int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
···
 int ipip_gue_set_tunnel(struct __sk_buff *skb)
 {
 	struct bpf_tunnel_key key = {};
-	struct bpf_fou_encap encap = {};
+	struct bpf_fou_encap___local encap = {};
 	void *data = (void *)(long)skb->data;
 	struct iphdr *iph = data;
 	void *data_end = (void *)(long)skb->data_end;
···
 	encap.sport = 0;
 	encap.dport = bpf_htons(5555);
 
-	ret = bpf_skb_set_fou_encap(skb, &encap, FOU_BPF_ENCAP_GUE);
+	ret = bpf_skb_set_fou_encap(skb, (struct bpf_fou_encap *)&encap,
+				    bpf_core_enum_value(enum bpf_fou_encap_type___local,
+							FOU_BPF_ENCAP_GUE___local));
 	if (ret < 0) {
 		log_err(ret);
 		return TC_ACT_SHOT;
···
 int ipip_fou_set_tunnel(struct __sk_buff *skb)
 {
 	struct bpf_tunnel_key key = {};
-	struct bpf_fou_encap encap = {};
+	struct bpf_fou_encap___local encap = {};
 	void *data = (void *)(long)skb->data;
 	struct iphdr *iph = data;
 	void *data_end = (void *)(long)skb->data_end;
···
 	encap.sport = 0;
 	encap.dport = bpf_htons(5555);
 
-	ret = bpf_skb_set_fou_encap(skb, &encap, FOU_BPF_ENCAP_FOU);
+	ret = bpf_skb_set_fou_encap(skb, (struct bpf_fou_encap *)&encap,
+				    FOU_BPF_ENCAP_FOU___local);
 	if (ret < 0) {
 		log_err(ret);
 		return TC_ACT_SHOT;
···
 {
 	int ret;
 	struct bpf_tunnel_key key = {};
-	struct bpf_fou_encap encap = {};
+	struct bpf_fou_encap___local encap = {};
 
 	ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
 	if (ret < 0) {
···
 		return TC_ACT_SHOT;
 	}
 
-	ret = bpf_skb_get_fou_encap(skb, &encap);
+	ret = bpf_skb_get_fou_encap(skb, (struct bpf_fou_encap *)&encap);
 	if (ret < 0) {
 		log_err(ret);
 		return TC_ACT_SHOT;