PPC: Make interrupts work

PPC: Make interrupts work

The interrupt code as is didn't really work for me. I couldn't even convince
Linux to take interrupt 9 in an interrupt-map.

So let's do this right. Let's map all PCI interrupts to 0x1b - 0x1e. That way
we're at least a small step closer to what real hardware does.

I also took the interrupt pin to line conversion from OpenBIOS, which at least
assures us we're compatible with our firmware :-).

A dump of the PCI interrupt-map from a U2 (iBook):

00009000 00000000 00000000 00000000 ff97c528 00000034 00000001
0000d800 00000000 00000000 00000000 ff97c528 0000003f 00000001
0000c000 00000000 00000000 00000000 ff97c528 0000001b 00000001
0000c800 00000000 00000000 00000000 ff97c528 0000001c 00000001
0000d000 00000000 00000000 00000000 ff97c528 0000001d 00000001

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>