iommu/vt-d: Detach domain before using a private one

When the default domain of a group doesn't work for a device,
the iommu driver will try to use a private domain. The domain
which was previously attached to the device must be detached.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Fixes: 942067f1 ("iommu/vt-d: Identify default domains replaced with private")
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lkml.org/lkml/2019/8/2/1379


Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>