vfio: Add header guards and includes to drivers/vfio/vfio.h

As is normal for headers.
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/1-v3-297af71838d2+b9-vfio_container_split_jgg@nvidia.comSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio.h

@@ -3,6 +3,14 @@
  * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
  *     Author: Alex Williamson <alex.williamson@redhat.com>
  */
+#ifndef __VFIO_VFIO_H__
+#define __VFIO_VFIO_H__
+
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/module.h>
+
+struct iommu_group;
 
 enum vfio_group_type {
 	/*
@@ -69,3 +77,5 @@ struct vfio_iommu_driver_ops {
 
 int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
 void vfio_unregister_iommu_driver(const struct vfio_iommu_driver_ops *ops);
+
+#endif