mfd: Add to_irq() member to asic3 gpio_chip structure

The gpio_to_irq() macro is now defined as __gpio_to_irq() instead of IRQ_GPIO().
The __gpio_to_irq() function returns -ENXIO if the referenced gpio_chip
structure does not define a to_irq() member.
This is true of the asic3 gpio_chip structure, and thus calls to gpio_to_irq()
now fail (for example from the gpio-vbus module).
This patch defines the to_irq() member in the asic3 gpio_chip structure.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/asic3.c

@@ -525,6 +525,11 @@ static void asic3_gpio_set(struct gpio_chip *chip,
 	return;
 }
 
+static int asic3_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
+{
+	return (offset < ASIC3_NUM_GPIOS) ? IRQ_BOARD_START + offset : -ENXIO;
+}
+
 static __init int asic3_gpio_probe(struct platform_device *pdev,
 				   u16 *gpio_config, int num)
 {
@@ -976,6 +981,7 @@ static int __init asic3_probe(struct platform_device *pdev)
 	asic->gpio.set = asic3_gpio_set;
 	asic->gpio.direction_input = asic3_gpio_direction_input;
 	asic->gpio.direction_output = asic3_gpio_direction_output;
+	asic->gpio.to_irq = asic3_gpio_to_irq;
 
 	ret = asic3_gpio_probe(pdev,
 			       pdata->gpio_config,