irqchip: renesas-irqc: Enable mask on suspend

Now when lazy interrupt disable has been enabled in the driver
then extend the code to set IRQCHIP_MASK_ON_SUSPEND which tells
the core that only IRQs marked as wakeups need to stay enabled
during Suspend-to-RAM.

Signed-off-by: Magnus Damm <damm@opensource.se>
Cc: rob.herring@calxeda.com
Cc: grant.likely@secretlab.ca
Cc: horms@verge.net.au
Link: http://lkml.kernel.org/r/20131204120556.29642.27021.sendpatchset@w520
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>