HID: logitech: Handle 0 scroll events for the m560

hidpp_scroll_counter_handle_scroll() doesn't expect a 0-value scroll event, it
gets interpreted as a negative scroll direction event. This can cause scroll
direction resets and thus broken scrolling.

Fixes: 4435ff2f ("HID: logitech: Enable high-resolution scrolling on Logitech mice")
Cc: stable@vger.kernel.org # v5.0
Reported-and-tested-by: Aimo Metsälä <aimetsal@outlook.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/hid-logitech-hidpp.c

@@ -2614,8 +2614,9 @@ static int m560_raw_event(struct hid_device *hdev, u8 *data, int size)
 		input_report_rel(mydata->input, REL_Y, v);
 
 		v = hid_snto32(data[6], 8);
-		hidpp_scroll_counter_handle_scroll(
-				&hidpp->vertical_wheel_counter, v);
+		if (v != 0)
+			hidpp_scroll_counter_handle_scroll(
+					&hidpp->vertical_wheel_counter, v);
 
 		input_sync(mydata->input);
 	}