i2c: st: use to_platform_device()

Use to_platform_device() instead of open-coding it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-st.c

@@ -708,8 +708,7 @@ static int st_i2c_xfer(struct i2c_adapter *i2c_adap,
 #ifdef CONFIG_PM_SLEEP
 static int st_i2c_suspend(struct device *dev)
 {
-	struct platform_device *pdev =
-		container_of(dev, struct platform_device, dev);
+	struct platform_device *pdev = to_platform_device(dev);
 	struct st_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 
 	if (i2c_dev->busy)