input: Add power button support for mc13783

This adds support for the power-on buttons of MC13783 PMIC.

Signed-off-by: Philippe Rétornaz <philippe.retornaz@epfl.ch>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/mc13xxx-core.c b/drivers/mfd/mc13xxx-core.c
index e55b221..edcd397 100644
--- a/drivers/mfd/mc13xxx-core.c
+++ b/drivers/mfd/mc13xxx-core.c
@@ -703,6 +703,11 @@
 	enum mc13xxx_id id;
 	int ret;
 
+	if (!pdata) {
+		dev_err(&spi->dev, "invalid platform data\n");
+		return -EINVAL;
+	}
+
 	mc13xxx = kzalloc(sizeof(*mc13xxx), GFP_KERNEL);
 	if (!mc13xxx)
 		return -ENOMEM;
@@ -763,6 +768,10 @@
 		mc13xxx_add_subdevice_pdata(mc13xxx, "%s-led",
 				pdata->leds, sizeof(*pdata->leds));
 
+	if (pdata->buttons)
+		mc13xxx_add_subdevice_pdata(mc13xxx, "%s-pwrbutton",
+				pdata->buttons, sizeof(*pdata->buttons));
+
 	return 0;
 }