gpiolib: use gpio_chips list in gpiolib_sysfs_init

Use the small list of GPIO chips instead of parsing the whole GPIO
number space.
Signed-off-by: NAlexandre Courbot <acourbot@nvidia.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/gpio/gpiolib.c

@@ -974,7 +974,7 @@ static int __init gpiolib_sysfs_init(void)
 {
 	int		status;
 	unsigned long	flags;
-	unsigned	gpio;
+	struct gpio_chip *chip;
 
 	status = class_register(&gpio_class);
 	if (status < 0)
@@ -987,10 +987,7 @@ static int __init gpiolib_sysfs_init(void)
 	 * registered, and so arch_initcall() can always gpio_export().
 	 */
 	spin_lock_irqsave(&gpio_lock, flags);
-	for (gpio = 0; gpio < ARCH_NR_GPIOS; gpio++) {
-		struct gpio_chip	*chip;
-
-		chip = gpio_desc[gpio].chip;
+	list_for_each_entry(chip, &gpio_chips, list) {
 		if (!chip || chip->exported)
 			continue;