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>
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 52c4461..73ce871 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -216,7 +216,7 @@
 	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
 };