mfd: Fix arizona-irq.c build by selecting REGMAP_IRQ

arizona-irq.c uses functions that are only available when
CONFIG_REGMAP_IRQ is enabled, so select that symbol for
arizona builds.

Fixes these build errors:

arizona-irq.c:(.text+0xb2d47): undefined reference to `regmap_irq_get_virq'
(.text+0xb2fe3): undefined reference to `regmap_add_irq_chip'
(.text+0xb3173): undefined reference to `regmap_del_irq_chip'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>