vfio: expose functions

vfio: expose functions

The following symbols are used by vfio implementations within the PCI bus.
They need to be publicly available for the PCI bus to be outside the
EAL.

  + vfio_enable;
  + vfio_is_enabled;
  + vfio_noiommu_is_enabled;
  + vfio_release_device;
  + vfio_setup_device;

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>