mfd: tps65912: Declare and use tps65912_irq_exit()

Clean up interrupts on exit, silencing a sparse warning caused by
tps65912_irq_exit() being defined but not prototyped as we go.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/tps65912-core.c b/drivers/mfd/tps65912-core.c
index 4658b5b..aeb8e40 100644
--- a/drivers/mfd/tps65912-core.c
+++ b/drivers/mfd/tps65912-core.c
@@ -169,6 +169,7 @@
 void tps65912_device_exit(struct tps65912 *tps65912)
 {
 	mfd_remove_devices(tps65912->dev);
+	tps65912_irq_exit(tps65912);
 	kfree(tps65912);
 }