gpio: pcf857x: fixup smatch WARNING

6e20a0a429bd4dc07d6de16d9c247270e04e4aa0
(gpio: pcf857x: enable gpio_to_irq() support)
added new smatch warnings

drivers/gpio/gpio-pcf857x.c:288 pcf857x_probe() error: we previously \
	assumed 'pdata' could be null (see line 277)
drivers/gpio/gpio-pcf857x.c:364 pcf857x_probe() warn: variable dereferenced\
	 before check 'pdata' (see line 292)
drivers/gpio/gpio-pcf857x.c:421 pcf857x_remove() error: we previously\
	 assumed 'pdata' could be null (see line 410)

This patch fixes it

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pcf857x.c

@@ -285,7 +285,7 @@ static int pcf857x_probe(struct i2c_client *client,
 	gpio->chip.ngpio		= id->driver_data;
 
 	/* enable gpio_to_irq() if platform has settings */
-	if (pdata->irq) {
+	if (pdata && pdata->irq) {
 		status = pcf857x_irq_domain_init(gpio, pdata, &client->dev);
 		if (status < 0) {
 			dev_err(&client->dev, "irq_domain init failed\n");
@@ -394,7 +394,7 @@ fail:
 	dev_dbg(&client->dev, "probe error %d for '%s'\n",
 			status, client->name);
 
-	if (pdata->irq)
+	if (pdata && pdata->irq)
 		pcf857x_irq_domain_cleanup(gpio);
 
 	kfree(gpio);
@@ -418,7 +418,7 @@ static int pcf857x_remove(struct i2c_client *client)
 		}
 	}
 
-	if (pdata->irq)
+	if (pdata && pdata->irq)
 		pcf857x_irq_domain_cleanup(gpio);
 
 	status = gpiochip_remove(&gpio->chip);