hw/s390x: Re-enable the pci-bridge device on s390x

hw/s390x: Re-enable the pci-bridge device on s390x

Commit e779e5c05a ("hw/pci-bridge: Add a Kconfig switch for the
normal PCI bridge") added a config switch for the pci-bridge, so
that the device is not included in the s390x target anymore (since
the pci-bridge is not really useful on s390x).

However, it seems like libvirt is still adding pci-bridge devices
automatically to the guests' XML definitions (when adding a PCI
device to a non-zero PCI bus), so these guests are now broken due
to the missing pci-bridge in the QEMU binary.

To avoid disruption of the users, let's re-enable the pci-bridge
device on s390x for the time being.

Message-ID: <20241024130405.62134-1-thuth@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>