pci-bridge/i82801b11: clear bridge registers on platform reset

pci-bridge/i82801b11: clear bridge registers on platform reset

The "i82801b11-bridge" device model is a descendant of "base-pci-bridge"
(TYPE_PCI_BRIDGE). However, unlike other similar devices, such as

- pci-bridge,
- pcie-pci-bridge,
- PCIE Root Port,
- xio3130 switch upstream and downstream ports,
- dec-21154-p2p-bridge,
- pbm-bridge,
- xilinx-pcie-root,

"i82801b11-bridge" does not clear the bridge specific registers at
platform reset.

This is a problem because devices on "i82801b11-bridge" continue to
respond to config space cycles after platform reset, when addressed with
the bus number that was previously programmed into the secondary bus
number register of "i82801b11-bridge". This error breaks OVMF's search for
extra (PXB) root buses, for example.

The device class reset method for "i82801b11-bridge" is currently NULL;
set it directly to pci_bridge_reset(), like the last three bridge models
in the above listing do.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: qemu-stable@nongnu.org
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1541839
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>