[NET]: Use NIP6_FMT in kernel.h

There are errors and inconsistency in the display of NIP6 strings.
	ie: net/ipv6/ip6_flowlabel.c

There are errors and inconsistency in the display of NIPQUAD strings too.
	ie: net/netfilter/nf_conntrack_ftp.c

This patch:
	adds NIP6_FMT to kernel.h
	changes all code to use NIP6_FMT
	fixes net/ipv6/ip6_flowlabel.c
	adds NIPQUAD_FMT to kernel.h
	fixes net/netfilter/nf_conntrack_ftp.c
	changes a few uses of "%u.%u.%u.%u" to NIPQUAD_FMT for symmetry to NIP6_FMT

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 305d9ee..cb8856b 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -692,7 +692,7 @@
 		if (!(neigh->nud_state & NUD_VALID)) {
 			ND_PRINTK1(KERN_DEBUG
 				   "%s(): trying to ucast probe in NUD_INVALID: "
-				   "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
+				   NIP6_FMT "\n",
 				   __FUNCTION__,
 				   NIP6(*target));
 		}