mfd: arizona: Fix lockdep recursion warning on set_irq_wake

Avoid a false recursive locking warning from lockdep by adding a lock
class for the arizona IRQ chip.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>