ipsec: move startup config to common file

The ipsec startup.conf config currently exists in ipsec_tun.c. This is
because currently the only ipsec{...} options are tunnel related.

This patch moves the ipsec config to a common file (ipsec.c) for future
extensibility/addition of non-tunnel related config options.

Type: refactor
Signed-off-by: Zachary Leaf <zachary.leaf@arm.com>
Change-Id: I1569dd7948334fd2cc28523ccc6791a22dea8d32
diff --git a/src/vnet/ipsec/ipsec_tun.h b/src/vnet/ipsec/ipsec_tun.h
index c79fb90..f452fa4 100644
--- a/src/vnet/ipsec/ipsec_tun.h
+++ b/src/vnet/ipsec/ipsec_tun.h
@@ -163,6 +163,9 @@
 extern void ipsec_tun_register_nodes (ip_address_family_t af);
 extern void ipsec_tun_unregister_nodes (ip_address_family_t af);
 
+extern void ipsec_tun_table_init (ip_address_family_t af, uword table_size,
+				  u32 n_buckets);
+
 /*
  * DP API
  */