This is more proper to use PCIE_MMCFG_BUS to retrieve end_bus_number.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Message-id: 20190312074953.16671-1-richardw.yang@linux.intel.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>