mfd: twl-core: Add IRQ_DOMAIN dependency

TWL4030 depends on IRQ_DOMAIN support, so this patch selects it in Kconfig.
It used to be that CONFIG_IRQ_DOMAIN must only be selected by the architecture,
but recent cleanups have fixed it so that it is safe to select from anywhere.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
[grant.likely: Changed from a depends to a select]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Samuel Ortiz <sameo@linux.intel.com>