apb: use normal PCI device header for PBM device

PBM has a normal PCI device header, fix.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/apb_pci.c b/hw/apb_pci.c
index 1d25da8..b10f31e 100644
--- a/hw/apb_pci.c
+++ b/hw/apb_pci.c
@@ -444,7 +444,6 @@
     k->vendor_id = PCI_VENDOR_ID_SUN;
     k->device_id = PCI_DEVICE_ID_SUN_SABRE;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
-    k->is_bridge = 1;
 }
 
 static TypeInfo pbm_pci_host_info = {