vfio: revert "iommu driver notify callback"

Revert this dead code:
commit ec5e32940cc9 ("vfio: iommu driver notify callback")

Signed-off-by: Steve Sistare <[e-mail]>
Reviewed-by: Kevin Tian <[e-mail]>
Reviewed-by: Jason Gunthorpe <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/container.c

···
 static int vfio_fops_release(struct inode *inode, struct file *filep)
 {
 	struct vfio_container *container = filep->private_data;
-	struct vfio_iommu_driver *driver = container->iommu_driver;
-
-	if (driver && driver->ops->notify)
-		driver->ops->notify(container->iommu_data,
-				    VFIO_IOMMU_CONTAINER_CLOSE);
 
 	filep->private_data = NULL;
 

drivers/vfio/vfio.h

···
 void vfio_group_cleanup(void);
 
 #if IS_ENABLED(CONFIG_VFIO_CONTAINER)
-/* events for the backend driver notify callback */
-enum vfio_iommu_notify_type {
-	VFIO_IOMMU_CONTAINER_CLOSE = 0,
-};
-
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
  */
···
 				  void *data, size_t count, bool write);
 	struct iommu_domain *(*group_iommu_domain)(void *iommu_data,
 						   struct iommu_group *group);
-	void		(*notify)(void *iommu_data,
-				  enum vfio_iommu_notify_type event);
 };
 
 struct vfio_iommu_driver {