USB: core: constify vm_operations_struct

vm_operations_struct are not supposed to change at runtime.
All functions working with const vm_operations_struct.
So mark the non-const structs as const.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/devio.c

@@ -210,7 +210,7 @@ static void usbdev_vm_close(struct vm_area_struct *vma)
 	dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
 }
 
-static struct vm_operations_struct usbdev_vm_ops = {
+static const struct vm_operations_struct usbdev_vm_ops = {
 	.open = usbdev_vm_open,
 	.close = usbdev_vm_close
 };