irqchip: exynos-combiner: Save IRQ enable set on suspend

The Exynos interrupt combiner IP loses its state when the SoC enters
into a low power state during a Suspend-to-RAM. This means that if a
IRQ is used as a source, the interrupts for the devices are disabled
when the system is resumed from a sleep state so are not triggered.

Save the interrupt enable set register for each combiner group and
restore it after resume to make sure that the interrupts are enabled.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Peter Chubb <peter.chubb@nicta.com.au>
Cc: Shuah Khan <shuahkhan@gmail.com>
Cc: Chanho Park <parkch98@gmail.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Link: http://lkml.kernel.org/r/1434087795-13990-1-git-send-email-javier.martinez@collabora.co.uk


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>