net: ipv4: ipconfig: fix unused variable

When CONFIG_PROC_FS isn't set, variable ipconfig_dir isn't used.
net/ipv4/ipconfig.c:167:31: warning: ‘ipconfig_dir’ defined but not used [-Wunused-variable]
static struct proc_dir_entry *ipconfig_dir;
^~~~~~~~~~~~
Move the declaration of ipconfig_dir inside the CONFIG_PROC_FS ifdef to
fix the warning.

Fixes: c04d2cb2009f ("ipconfig: Write NTP server IPs to /proc/net/ipconfig/ntp_servers")
Signed-off-by: Anders Roxell <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ipconfig.c

···
  * Private state.
  */
 
-/* proc_dir_entry for /proc/net/ipconfig */
-static struct proc_dir_entry *ipconfig_dir;
-
 /* Name of user-selected boot device */
 static char user_dev_name[IFNAMSIZ] __initdata = { 0, };
 
···
 #endif /* IPCONFIG_DYNAMIC */
 
 #ifdef CONFIG_PROC_FS
+/* proc_dir_entry for /proc/net/ipconfig */
+static struct proc_dir_entry *ipconfig_dir;
 
 /* Name servers: */
 static int pnp_seq_show(struct seq_file *seq, void *v)