pinctrl: core: Warn about NULL gpio_chip in pinctrl_ready_for_gpio_range()

If the gpio driver is confused about the numbers for gpio-ranges,
pinctrl_ready_for_gpio_range() may get called with invalid GPIO
causing a NULL pointer exception. Let's instead provide a warning
that allows fixing the problem and return with error.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.c

@@ -349,6 +349,9 @@ static bool pinctrl_ready_for_gpio_range(unsigned gpio)
 	struct pinctrl_gpio_range *range = NULL;
 	struct gpio_chip *chip = gpio_to_chip(gpio);
 
+	if (WARN(!chip, "no gpio_chip for gpio%i?", gpio))
+		return false;
+
 	mutex_lock(&pinctrldev_list_mutex);
 
 	/* Loop over the pin controllers */