powerpc/irq: Convert obsolete hw_interrupt_type to struct irq_chip

Impact: cleanup

Convert the last remaining users to struct irq_chip.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: linuxppc-dev@ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>