Add a subclass of the PCI-PCI bridge driver that uses the PCIBIOS to
route interrupts if the child bus is described in the PCIBIOS interrupt
routing table. For child busses that are in the routing table, they do
not necessarily use a 'swizzle' on their pins on the parent bus to route
interrupts for child devices. If the child bus is an embedded device then
the pins on the child devices can be (and usually are) directly connected
either to a PIC or to a Interrupt Router. This fixes PCIBIOS interrupt
routing across PCI-PCI bridges for embedded devices.