[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/icmp.c b/net/ipv6/icmp.c
index 53c81fc..fcf8831 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -607,7 +607,7 @@
 		skb->csum = ~csum_ipv6_magic(saddr, daddr, skb->len,
 					     IPPROTO_ICMPV6, 0);
 		if (__skb_checksum_complete(skb)) {
-			LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 checksum failed [%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x > %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x]\n",
+			LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 checksum failed [" NIP6_FMT " > " NIP6_FMT "]\n",
 				       NIP6(*saddr), NIP6(*daddr));
 			goto discard_it;
 		}