staging: gasket: apex return error on sysfs show of missing attribute

Apex sysfs show function return -ENODEV if the attribute is not present,
rather than silently failing from the standpoint of the userspace
accessor.
Reported-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gasket/apex_driver.c

@@ -710,14 +710,14 @@ static ssize_t sysfs_show(
 	gasket_dev = gasket_sysfs_get_device_data(device);
 	if (!gasket_dev) {
 		gasket_nodev_error("No Apex device sysfs mapping found");
-		return 0;
+		return -ENODEV;
 	}
 
 	gasket_attr = gasket_sysfs_get_attr(device, attr);
 	if (!gasket_attr) {
 		gasket_nodev_error("No Apex device sysfs attr data found");
 		gasket_sysfs_put_device_data(device, gasket_dev);
-		return 0;
+		return -ENODEV;
 	}
 
 	type = (enum sysfs_attribute_type)gasket_sysfs_get_attr(device, attr);