leds-gpio: fix possible crash on OF device unbinding

If there are leds present in the OF tree, but the GPIOs for (some) of
them are unavailable, led_data doesn't get populated with correct
devices. Then, on device unbinding, one can crash the kernel.

Workaround this by setting led->gpio to invalid value early.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/leds/leds-gpio.c

@@ -78,6 +78,8 @@ static int __devinit create_gpio_led(const struct gpio_led *template,
 {
 	int ret, state;
 
+	led_dat->gpio = -1;
+
 	/* skip leds that aren't available */
 	if (!gpio_is_valid(template->gpio)) {
 		printk(KERN_INFO "Skipping unavailable LED gpio %d (%s)\n",