esp: Add gso handlers for esp4 and esp6

This patch extends the xfrm_type by an encap function pointer
and implements esp4_gso_encap and esp6_gso_encap. These functions
doing the basic esp encapsulation for a GSO packet. In case the
GSO packet needs to be segmented in software, we add gso_segment
functions. This codepath is going to be used on esp hardware
offloads.

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

net/xfrm/xfrm_replay.c

@@ -45,7 +45,8 @@ u32 xfrm_replay_seqhi(struct xfrm_state *x, __be32 net_seq)
 
 	return seq_hi;
 }
-
+EXPORT_SYMBOL(xfrm_replay_seqhi);
+;
 static void xfrm_replay_notify(struct xfrm_state *x, int event)
 {
 	struct km_event c;