xen-pt: Fix PCI devices re-attach failed

xen-pt: Fix PCI devices re-attach failed

Use the 'xl pci-attach $DomU $BDF' command to attach more than
one PCI devices to the guest, then detach the devices with
'xl pci-detach $DomU $BDF', after that, re-attach these PCI
devices again, an error message will be reported like following:

    libxl: error: libxl_qmp.c:287:qmp_handle_error_response: receive
    an error message from QMP server: Duplicate ID 'pci-pt-03_10.1'
    for device.

If using the 'address_space_memory' as the parameter of
'memory_listener_register', 'xen_pt_region_del' will not be called
if the memory region's name is not 'xen-pci-pt-*' when the devices
is detached. This will cause the device's related QemuOpts object
not be released properly.

Using the device's address space can avoid such issue, because the
calling count of 'xen_pt_region_add' when attaching and the calling
count of 'xen_pt_region_del' when detaching is the same, so all the
memory region ref and unref by the 'xen_pt_region_add' and
'xen_pt_region_del' can be released properly.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Longtao Pang <longtaox.pang@intel.com>