ipv6: frags: fix /proc/sys/net/ipv6/ip6frag_low_thresh

I forgot to change ip6frag_low_thresh proc_handler
from proc_dointvec_minmax to proc_doulongvec_minmax

Fixes: 3e67f106 ("inet: frags: break the 2GB limit for frags storage")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/reassembly.c

@@ -564,7 +564,7 @@ static struct ctl_table ip6_frags_ns_ctl_table[] = {
 		.data		= &init_net.ipv6.frags.low_thresh,
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= proc_doulongvec_minmax,
 		.extra1		= &zero,
 		.extra2		= &init_net.ipv6.frags.high_thresh
 	},