mfd: Set MAX8997 irq pointer

Required platform information is not handed to max8997-irq.c properly.
This patch enables to hand over such information to max8997-irq.c so
that max8997-irq functions properly.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>