mfd: max8998: Add irq domain support

This patch adds irq domain support for max8998 interrupts.

To keep both non-DT and DT worlds happy, simple domain is used, which is
linear when no explicit IRQ base is specified and legacy, with static
mapping, otherwise.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/include/linux/mfd/max8998.h b/include/linux/mfd/max8998.h
index 6823548..7547118 100644
--- a/include/linux/mfd/max8998.h
+++ b/include/linux/mfd/max8998.h
@@ -100,7 +100,7 @@
 struct max8998_platform_data {
 	struct max8998_regulator_data	*regulators;
 	int				num_regulators;
-	int				irq_base;
+	unsigned int			irq_base;
 	int				ono;
 	bool				buck_voltage_lock;
 	int				buck1_voltage1;