gpio: sysfs: fix memory leak in gpiod_sysfs_set_active_low

commit 49d2ca84 upstream.

Fix memory leak in the gpio sysfs interface due to failure to drop
reference to device returned by class_find_device when setting the
gpio-line polarity.

Fixes: 07697461 ("gpiolib: add support for changing value polarity
in sysfs")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpio/gpiolib.c

@@ -872,7 +872,7 @@ int gpio_sysfs_set_active_low(unsigned gpio, int value)
 	}
 
 	status = sysfs_set_active_low(desc, dev, value);
-
+	put_device(dev);
 unlock:
 	mutex_unlock(&sysfs_lock);