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>

include/linux/mfd/max8998-private.h

@@ -132,6 +132,8 @@ enum {
 
 #define MAX8998_ENRAMP                  (1 << 4)
 
+struct irq_domain;
+
 /**
  * struct max8998_dev - max8998 master device for sub-drivers
  * @dev: master device of the chip (can be used to access platform data)
@@ -153,7 +155,8 @@ struct max8998_dev {
 	struct mutex iolock;
 	struct mutex irqlock;
 
-	int irq_base;
+	unsigned int irq_base;
+	struct irq_domain *irq_domain;
 	int irq;
 	int ono;
 	u8 irq_masks_cur[MAX8998_NUM_IRQ_REGS];

include/linux/mfd/max8998.h

@@ -100,7 +100,7 @@ struct max8998_regulator_data {
 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;