xen/arm: allow PCI host bridge to have private data

Some of the PCI host bridges require private data. Add priv field
to struct pci_host_bridge, so such bridges may populate it with
their private data.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/include/asm/pci.h

@@ -68,6 +68,7 @@ struct pci_host_bridge {
     uint16_t segment;                /* Segment number */
     struct pci_config_window* cfg;   /* Pointer to the bridge config window */
     const struct pci_ops *ops;
+    void *priv;                      /* Private data of the bridge. */
 };
 
 struct pci_ops {