powerpc/ps3: Use smp_request_message_ipi

ps3 has 4 ipis per cpu and can use the new smp_request_message_ipi to
reduce path length when receiving an ipi.

This has the side effect of setting IRQF_PERCPU.

Signed-off-by: Milton Miller <miltonm@bga.com>
Acked-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>