[POWERPC] Fix pci domain detection

[POWERPC] Fix pci domain detection

The /proc/bus/pci/* files list PCI domain numbers only for
devices that claim to be on a multi-domain system. The check
for this is broken on powerpc, because the buid value is
truncated to 32 bits.

There is at least one machine (IBM QS21) that only uses
the high-order bits of the buid, so the return value
of pci_proc_domain() ends up being always zero, which
makes /proc/bus/pci useless.

Change the logic to always return '1' for a nonzero
buid value.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>