vfio: enable unmapping resource for secondary

vfio: enable unmapping resource for secondary

Subroutine to unmap VFIO resource is shared by secondary and
primary, and it does not work on the secondary process. Since
for secondary process, it is not necessary to close interrupt
handler, set pci bus mastering and remove vfio_res from
vfio_res_list. So, the patch adds a dedicate function to handle
the situation when a device is unmapped on a secondary process.

Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>