[IPV6] ADDRCONF: Fix array size for sysctls.

We have been using __NET_IPV6_MAX for adjusting the size of array
for sysctl table, but it does not work any longer because of the
deprecation of NET_IPV6_xxx constants.  Let's use DEVCONF_MAX
instead.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

net/ipv6/addrconf.c

@@ -3877,7 +3877,7 @@ static int addrconf_sysctl_forward_strategy(ctl_table *table,
 static struct addrconf_sysctl_table
 {
 	struct ctl_table_header *sysctl_header;
-	ctl_table addrconf_vars[__NET_IPV6_MAX];
+	ctl_table addrconf_vars[DEVCONF_MAX+1];
 	char *dev_name;
 } addrconf_sysctl __read_mostly = {
 	.sysctl_header = NULL,