mfd: fix da903x warning

The da903x interrupt handler is retruning an int instead of an irqreturn_t.
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

drivers/mfd/da903x.c

@@ -413,7 +413,7 @@ static void da903x_irq_work(struct work_struct *work)
 	enable_irq(chip->client->irq);
 }
 
-static int da903x_irq_handler(int irq, void *data)
+static irqreturn_t da903x_irq_handler(int irq, void *data)
 {
 	struct da903x_chip *chip = data;