gpiolib: Hook up WM8994 gpio_to_irq()

Not sure where this went.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/gpio/wm8994-gpio.c b/drivers/gpio/wm8994-gpio.c
index 2ac9a16..618398e 100644
--- a/drivers/gpio/wm8994-gpio.c
+++ b/drivers/gpio/wm8994-gpio.c
@@ -140,6 +140,7 @@
 	.get			= wm8994_gpio_get,
 	.direction_output	= wm8994_gpio_direction_out,
 	.set			= wm8994_gpio_set,
+	.to_irq			= wm8994_gpio_to_irq,
 	.dbg_show		= wm8994_gpio_dbg_show,
 	.can_sleep		= 1,
 };