compat: Remove unused function

The compat function rpl_nf_conntrack_in() does not appear to be used
anywhere and emits warnings as such during builds < 4.10.

The patch passes Travis:

https://travis-ci.org/gvrose8192/ovs-experimental/builds/423097292

Remove it.

A backport of this patch to branch-2.10 seems to be required
to fix build errors when compiling against v3.16.54

  before: https://travis-ci.org/openvswitch/ovs/builds/602518689
  after: https://travis-ci.org/horms2/ovs/builds/602665800

Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

datapath/linux/compat/include/net/netfilter/nf_conntrack_core.h

@@ -67,27 +67,6 @@ static inline bool rpl_nf_ct_get_tuple(const struct sk_buff *skb,
 #define nf_ct_get_tuple rpl_nf_ct_get_tuple
 #endif /* HAVE_NF_CT_GET_TUPLEPR_TAKES_STRUCT_NET */
 
-/* Commit 08733a0cb7de ("netfilter: handle NF_REPEAT from nf_conntrack_in()")
- * introduced behavioural changes to this function which cannot be detected
- * in the headers. Unconditionally backport to kernels older than the one which
- * contains this commit. */
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4,10,0)
-static unsigned int rpl_nf_conntrack_in(struct net *net, u_int8_t pf,
-					unsigned int hooknum,
-					struct sk_buff *skb)
-{
-	int err;
-
-	/* Repeat if requested, see nf_iterate(). */
-	do {
-		err = nf_conntrack_in(net, pf, hooknum, skb);
-	} while (err == NF_REPEAT);
-
-	return err;
-}
-#define nf_conntrack_in rpl_nf_conntrack_in
-#endif /* < 4.10 */
-
 #ifdef HAVE_NF_CONN_TIMER
 
 #ifndef HAVE_NF_CT_DELETE