[POWERPC] Assign all PCI busses on G3 Blue & White

G3 Blue & White is misconfigured by default so that CardBus controllers
in PCI slots don't work.  The PCI bridge is programmed to only allow
access to bus 1 but not higher busses.

The patch forces the PCI busses to be reassigned if a Grackle controller
is found and the machine identifies itself as "PowerMac1,1"

Signed-off-by: Pavel Roskin <proski@gnu.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>