[SK_BUFF]: Introduce ipv6_hdr(), remove skb->nh.ipv6h

Now the skb->nh union has just one member, .raw, i.e. it is just like the
skb->mac union, strange, no? I'm just leaving it like that till the transport
layer is done with, when we'll rename skb->mac.raw to skb->mac_header (or
->mac_header_offset?), ditto for ->{h,nh}.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_rsvp.h

@@ -143,7 +143,7 @@ static int rsvp_classify(struct sk_buff *skb, struct tcf_proto *tp,
 	u8 tunnelid = 0;
 	u8 *xprt;
 #if RSVP_DST_LEN == 4
-	struct ipv6hdr *nhptr = skb->nh.ipv6h;
+	struct ipv6hdr *nhptr = ipv6_hdr(skb);
 #else
 	struct iphdr *nhptr = ip_hdr(skb);
 #endif