[IPV6]: fix flowlabel seqfile handling

There's a bug in the seqfile show operation for flowlabel objects, where 
each hash chain is traversed cumulatively for each element.  The following 
function is called for each element of each chain:

static void ip6fl_fl_seq_show(struct seq_file *seq, struct ip6_flowlabel *fl)
{
        while(fl) {
                seq_printf...
		
		fl = fl->next;
	}
}

Thus, objects can appear mutliple times when reading 
/proc/net/ip6_flowlabel, as the above is called for each element in the 
chain.

The solution is to remove the while() loop from the above, and traverse 
each chain exactly once, per the patch below.  This also removes the 
ip6fl_fl_seq_show() function, which does nothing else.

Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>