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>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>