pci: Remove unused mem_base from PCIBus

Obsoleted by f64e02b6cc.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/pci_internals.h b/hw/pci_internals.h
index c7fd23d..10b4adf 100644
--- a/hw/pci_internals.h
+++ b/hw/pci_internals.h
@@ -24,7 +24,6 @@
     void *irq_opaque;
     PCIDevice *devices[PCI_SLOT_MAX * PCI_FUNC_MAX];
     PCIDevice *parent_dev;
-    target_phys_addr_t mem_base;
     MemoryRegion *address_space_mem;
     MemoryRegion *address_space_io;