ipsec: Create and use new helpers for dst child access.

This will make a future change moving the dst->child pointer less
invasive.

Signed-off-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 4021b49..4c08eb0 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1004,6 +1004,11 @@
 }
 
 #ifdef CONFIG_XFRM
+static inline void xfrm_dst_set_child(struct xfrm_dst *xdst, struct dst_entry *child)
+{
+	xdst->u.dst.child = child;
+}
+
 static inline void xfrm_dst_destroy(struct xfrm_dst *xdst)
 {
 	xfrm_pols_put(xdst->pols, xdst->num_pols);