mfd: twl4030: Allow IRQ wake enable to succeed on subchip IRQs

The genirq IRQ wake method will default to failure if the irq_chip
does not provide a set_wake method.  However, for TWL4030 sub-chip
IRQs, we want the wake enable to succeed even though we don't provide
a set_wake method.  This allows sub-chip IRQs to still be flagged as
wakeup capable, and allow them to wakeup from suspend (or abort
suspend if they fire during suspend.)

To fix, use the IRQCHIP_SKIP_SET_WAKE flag in the irq_chip.

Signed-off-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>