mfd: Add IRQ domain support for the AB8500

As the AB8500 is an IRQ controller in its own right, here we provide
the AB8500 driver with IRQ domain support. This is required if we wish
to reference any of its IRQs from a platform's Device Tree.

Cc: Naga Radheshy <naga.radheshy@stericsson.com>
Cc: Mattias Wallin <mattias.wallin@stericsson.com>
Cc: Daniel Willerud <daniel.willerud@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index ed488ed..8b56c19 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -709,6 +709,7 @@
 	bool "ST-Ericsson AB8500 Mixed Signal Power Management chip"
 	depends on GENERIC_HARDIRQS && ABX500_CORE && MFD_DB8500_PRCMU
 	select MFD_CORE
+	select IRQ_DOMAIN
 	help
 	  Select this option to enable access to AB8500 power management
 	  chip. This connects to U8500 either on the SSP/SPI bus (deprecated