udp/udplite: Remove unused function declarations udp{,lite}_get_port()

Commit 6ba5a3c5

 ("[UDP]: Make full use of proto.h.udp_hash innovation.")
removed these implementations but leave declarations.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>