ipv6 addrconf: revert /proc/net/if_inet6 ifa_flag format

Turned out that applications like ifconfig do not handle the change.
So revert ifa_flag format back to 2-letter hex value.

Introduced by:
commit 479840ff
    "ipv6 addrconf: extend ifa_flags to u32"
Reported-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Tested-by: NFLorent Fourcot <florent.fourcot@enst-bretagne.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -3367,12 +3367,12 @@ static void if6_seq_stop(struct seq_file *seq, void *v)
 static int if6_seq_show(struct seq_file *seq, void *v)
 {
 	struct inet6_ifaddr *ifp = (struct inet6_ifaddr *)v;
-	seq_printf(seq, "%pi6 %02x %02x %02x %03x %8s\n",
+	seq_printf(seq, "%pi6 %02x %02x %02x %02x %8s\n",
 		   &ifp->addr,
 		   ifp->idev->dev->ifindex,
 		   ifp->prefix_len,
 		   ifp->scope,
-		   ifp->flags,
+		   (u8) ifp->flags,
 		   ifp->idev->dev->name);
 	return 0;
 }