40p: use OR gate to wire up raven PCI interrupts

40p: use OR gate to wire up raven PCI interrupts

According to the PReP specification section 6.1.6 "System Interrupt
Assignments", all PCI interrupts are routed via IRQ 15.

Instead of mapping each PCI IRQ separately, we introduce an OR gate within the
raven PCI host bridge and then wire the single output of the OR gate to the
interrupt controller.

Note that whilst the (now deprecated) PReP machine still exists we still need
to preserve the old IRQ routing. This is done by adding a new "is-legacy-prep"
property to the raven PCI host bridge which is set to true for the PReP
machine.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Hervé Poussineau <hpoussin@reactos.org>
Tested-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>