pci: make sure pci_bus_is_express() won't error out with "discards ‘const’ qualifier"

function doesn't need RW aceess to passed in bus pointer,
make it const.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20230112140312.3096331-31-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pci.c

@@ -483,7 +483,7 @@ static void pci_bus_uninit(PCIBus *bus)
     pci_host_bus_unregister(BUS(bus)->parent);
 }
 
-bool pci_bus_is_express(PCIBus *bus)
+bool pci_bus_is_express(const PCIBus *bus)
 {
     return object_dynamic_cast(OBJECT(bus), TYPE_PCIE_BUS);
 }

include/hw/pci/pci.h

@@ -270,7 +270,7 @@ typedef void (*pci_bus_dev_fn)(PCIBus *b, PCIDevice *d, void *opaque);
 typedef void (*pci_bus_fn)(PCIBus *b, void *opaque);
 typedef void *(*pci_bus_ret_fn)(PCIBus *b, void *opaque);
 
-bool pci_bus_is_express(PCIBus *bus);
+bool pci_bus_is_express(const PCIBus *bus);
 
 void pci_root_bus_init(PCIBus *bus, size_t bus_size, DeviceState *parent,
                        const char *name,