bpf: sockhash, add release routine

Add map_release_uref pointer to hashmap ops. This was dropped when
original sockhash code was ported into bpf-next before initial
commit.

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

kernel/bpf/sockmap.c

@@ -2496,6 +2496,7 @@ const struct bpf_map_ops sock_hash_ops = {
 	.map_get_next_key = sock_hash_get_next_key,
 	.map_update_elem = sock_hash_update_elem,
 	.map_delete_elem = sock_hash_delete_elem,
+	.map_release_uref = sock_map_release,
 };
 
 BPF_CALL_4(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock,