xfrm4: Remove xfrm_tunnel_notifier

This was used from vti and is replaced by the IPsec protocol
multiplexer hooks. It is now unused, so remove it.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -1531,8 +1531,6 @@ int xfrm4_protocol_deregister(struct xfrm4_protocol *handler, unsigned char prot
 int xfrm4_tunnel_register(struct xfrm_tunnel *handler, unsigned short family);
 int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler, unsigned short family);
 void xfrm4_local_error(struct sk_buff *skb, u32 mtu);
-int xfrm4_mode_tunnel_input_register(struct xfrm_tunnel_notifier *handler);
-int xfrm4_mode_tunnel_input_deregister(struct xfrm_tunnel_notifier *handler);
 int xfrm6_mode_tunnel_input_register(struct xfrm_tunnel_notifier *handler);
 int xfrm6_mode_tunnel_input_deregister(struct xfrm_tunnel_notifier *handler);
 int xfrm6_extract_header(struct sk_buff *skb);