The imx6 PM code seems to be quite creative in its use of irq_data,
using something that is very much a hardware interrupt number where
we expect a virtual one.  Yes, it worked so far, but that's only
luck, and it will definitely explode in 3.19.

Fix it by using a pair of helper functions that deal with the
actual hardware.
Tested-by: NFabio Estevam <fabio.estevam@freescale.com>
Acked-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NOlof Johansson <olof@lixom.net>