vfio: Update the kdoc for vfio_device_ops

this is missed when adding bind_iommufd/unbind_iommufd and attach_ioas.
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20230209081210.141372-2-yi.l.liu@intel.comSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

include/linux/vfio.h

@@ -70,6 +70,10 @@ struct vfio_device {
  *
  * @init: initialize private fields in device structure
  * @release: Reclaim private fields in device structure
+ * @bind_iommufd: Called when binding the device to an iommufd
+ * @unbind_iommufd: Opposite of bind_iommufd
+ * @attach_ioas: Called when attaching device to an IOAS/HWPT managed by the
+ *		 bound iommufd. Undo in unbind_iommufd.
  * @open_device: Called when the first file descriptor is opened for this device
  * @close_device: Opposite of open_device
  * @read: Perform read(2) on device file descriptor