libbpf: Always use libbpf_err to return an error in bpf_xdp_query()

In order to properly set errno, rely on libbpf_err utility routine in
bpf_xdp_query() to return an error to the caller.

Fixes: 04d58f1b ("libbpf: add API to get XDP/XSK supported features")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/827d40181f9f90fb37702f44328e1614df7c0503.1675768112.git.lorenzo@kernel.org

tools/lib/bpf/netlink.c

@@ -480,7 +480,7 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
 
 	err = nlattr_add(&req, NETDEV_A_DEV_IFINDEX, &ifindex, sizeof(ifindex));
 	if (err < 0)
-		return err;
+		return libbpf_err(err);
 
 	err = libbpf_netlink_send_recv(&req, NETLINK_GENERIC,
 				       parse_xdp_features, NULL, &md);