xen: Use the PCI_DEVICE macro

xen: Use the PCI_DEVICE macro

TYPE_XEN_PT_DEVICE is a subclass of TYPE_PCI_DEVICE, the clean way
to access the PCIDevice pointer is using the PCI_DEVICE() macro.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20180705155811.20366-4-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>