ipconfig: add static to local variable

ic_dev_xid is only used in ipconfig.c

Cc: "David S. Miller" <[e-mail]>
Cc: Alexey Kuznetsov <[e-mail]>
Cc: [e-mail]
Signed-off-by: Fabian Frederick <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ipconfig.c

···
 __be32 root_server_addr = NONE;	/* Address of NFS server */
 u8 root_server_path[256] = { 0, };	/* Path to mount as root */
 
-__be32 ic_dev_xid;		/* Device under configuration */
+static __be32 ic_dev_xid;		/* Device under configuration */
 
 /* vendor class identifier */
 static char vendor_class_identifier[253] __initdata;