xfrm: Remove unused function declarations

commit a269fbf ("xfrm: state: remove extract_input indirection from xfrm_state_afinfo")
left behind this.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

Author: Yue Haibing

include/net/xfrm.h

@@ -1669,7 +1669,6 @@ int pktgen_xfrm_outer_mode_output(struct xfrm_state *x, struct sk_buff *skb);
 #endif
 
 void xfrm_local_error(struct sk_buff *skb, int mtu);
-int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb);
 int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
 		    int encap_type);
 int xfrm4_transport_finish(struct sk_buff *skb, int async);
@@ -1689,7 +1688,6 @@ 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 xfrm6_extract_input(struct xfrm_state *x, struct sk_buff *skb);
 int xfrm6_rcv_spi(struct sk_buff *skb, int nexthdr, __be32 spi,
 		  struct ip6_tnl *t);
 int xfrm6_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,