ipv6: Fix the link time qualifier of 'ping_v6_proc_exit_net()'

The '.exit' functions from 'pernet_operations' structure should be marked
as __net_exit, not __net_init.

Fixes: d862e5461423 ("net: ipv6: Implement /proc/net/icmp6.")
Signed-off-by: Christophe JAILLET <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv6/ping.c

···
 	return 0;
 }
 
-static void __net_init ping_v6_proc_exit_net(struct net *net)
+static void __net_exit ping_v6_proc_exit_net(struct net *net)
 {
 	remove_proc_entry("icmp6", net->proc_net);
 }