gpiolib: Unify expectations about ->request() returned value

Half of the code in the GPIO library is written in an expectation that
any non-zero value returned from the ->request() callback is an error code,
while some code checks only for negative values.

Unify expectations about ->request() returned value to be non-zero
for an error and 0 for the success.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 728f6c6..26c5466 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -476,7 +476,7 @@ static ssize_t export_store(struct class *class,
 	 */
 
 	status = gpiod_request(desc, "sysfs");
-	if (status < 0) {
+	if (status) {
 		if (status == -EPROBE_DEFER)
 			status = -ENODEV;
 		goto done;