- Added vfio_device_get_from_dev() as wrapper to get
  reference to vfio_device from struct device.

- Added vfio_device_data() as a wrapper to get device_data from
  vfio_device.
Signed-off-by: NVijay Mohan Pandarathil <vijaymohan.pandarathil@hp.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>