HID: logitech: Prevent possibility of infinite loop when using /sys interface

If the device data is not accessible for some reason, returning 0 will cause the call to be
continuously called again as none of the string has been 'consumed'.

Signed-off-by: Simon Wood <simon@mungewell.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index cc2bd20..7835717 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -451,13 +451,13 @@
 	drv_data = hid_get_drvdata(hid);
 	if (!drv_data) {
 		hid_err(hid, "Private driver data not found!\n");
-		return 0;
+		return -EINVAL;
 	}
 
 	entry = drv_data->device_props;
 	if (!entry) {
 		hid_err(hid, "Device properties not found!\n");
-		return 0;
+		return -EINVAL;
 	}
 
 	if (range == 0)