pci: don't map usb host adapters above 4G

Otherwise our xhci driver has trouble accessing the mmio registers.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
index 950b089..c40375b 100644
--- a/src/fw/pciinit.c
+++ b/src/fw/pciinit.c
@@ -579,6 +579,8 @@
     hlist_for_each_entry_safe(entry, n, &from->list, node) {
         if (!entry->is64)
             continue;
+        if (entry->dev->class == PCI_CLASS_SERIAL_USB)
+            continue;
         // Move from source list to destination list.
         hlist_del(&entry->node);
         hlist_add(&entry->node, last);