usb: devio: declare usbdev_vm_ops as static

usbdev_vm_ops is used in devio.c only, so declare it as static
Signed-off-by: Michele Curti <michele.curti@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/devio.c

@@ -216,7 +216,7 @@ static void usbdev_vm_close(struct vm_area_struct *vma)
 	dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
 }
 
-struct vm_operations_struct usbdev_vm_ops = {
+static struct vm_operations_struct usbdev_vm_ops = {
 	.open = usbdev_vm_open,
 	.close = usbdev_vm_close
 };