intel-iommu: fix PCI device detach from virtual machine

When assign a device behind conventional PCI bridge or PCIe to
PCI/PCI-x bridge to a domain, it must assign its bridge and may
also need to assign secondary interface to the same domain.

Dependent assignment is already there, but dependent
deassignment is missed when detach device from virtual machine.
This results in conventional PCI device assignment failure after
it has been assigned once. This patch addes dependent
deassignment, and fixes the issue.

Signed-off-by: Weidong Han <weidong.han@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>