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 <florian@openwrt.org>
CC: stable@kernel.org
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/gpio/rdc321x-gpio.c

@@ -135,7 +135,7 @@ static int __devinit rdc321x_gpio_probe(struct platform_device *pdev)
 	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;