gpio: Fix null pointer dereference while accessing rdc321x platform_data

rdc321x-gpio currently fetches its driver specific data by using the
platform_device->platform_data pointer, this is wrong because the mfd
device which registers our platform_device has been added using
mfd_add_device() which sets the platform_device->driver_data pointer
instead.

Signed-off-by: Florian Fainelli <[e-mail]>
CC: [e-mail]
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/gpio/rdc321x-gpio.c

···
 	struct rdc321x_gpio *rdc321x_gpio_dev;
 	struct rdc321x_gpio_pdata *pdata;
 
-	pdata = pdev->dev.platform_data;
+	pdata = platform_get_drvdata(pdev);
 	if (!pdata) {
 		dev_err(&pdev->dev, "no platform data supplied\n");
 		return -ENODEV;