kernel: re-add export ipv6_push_frag_opts for tunneling now patch

The patch got removed by commit 7dca1bae82 (kernel: bump to 4.9.105)
but is still required as ipv6_push_frag_opts needs to be exported.

Signed-off-by: Hans Dedecker <[email protected]>

target/linux/generic/backport-4.9/094-v4.12-0002-ipv6-Need-to-export-ipv6_push_frag_opts-for-tunnelin.patch

@@ -0,0 +1,31 @@
+From 5b8481fa42ac58484d633b558579e302aead64c1 Mon Sep 17 00:00:00 2001
+From: "David S. Miller" <[email protected]>
+Date: Mon, 1 May 2017 15:10:20 -0400
+Subject: [PATCH] ipv6: Need to export ipv6_push_frag_opts for tunneling now.
+
+Since that change also made the nfrag function not necessary
+for exports, remove it.
+
+Fixes: 89a23c8b528b ("ip6_tunnel: Fix missing tunnel encapsulation limit option")
+Signed-off-by: David S. Miller <[email protected]>
+---
+ net/ipv6/exthdrs.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/net/ipv6/exthdrs.c
++++ b/net/ipv6/exthdrs.c
+@@ -729,13 +729,13 @@ void ipv6_push_nfrag_opts(struct sk_buff
+ 	if (opt->hopopt)
+ 		ipv6_push_exthdr(skb, proto, NEXTHDR_HOP, opt->hopopt);
+ }
+-EXPORT_SYMBOL(ipv6_push_nfrag_opts);
+ 
+ void ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, u8 *proto)
+ {
+ 	if (opt->dst1opt)
+ 		ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst1opt);
+ }
++EXPORT_SYMBOL(ipv6_push_frag_opts);
+ 
+ struct ipv6_txoptions *
+ ipv6_dup_options(struct sock *sk, struct ipv6_txoptions *opt)