Input: elantech - fix semi-mt protocol for v3 HW

When the v3 hardware sees more than one finger, it uses the semi-mt
protocol to report the touches. However, it currently works when
num_fingers is 0, 1 or 2, but when it is 3 and above, it sends only 1
finger as if num_fingers was 1.

This confuses userspace which knows how to deal with extra fingers
when all the slots are used, but not when some are missing.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=90101

Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/elantech.c

@@ -315,7 +315,7 @@ static void elantech_report_semi_mt_data(struct input_dev *dev,
 					 unsigned int x2, unsigned int y2)
 {
 	elantech_set_slot(dev, 0, num_fingers != 0, x1, y1);
-	elantech_set_slot(dev, 1, num_fingers == 2, x2, y2);
+	elantech_set_slot(dev, 1, num_fingers >= 2, x2, y2);
 }
 
 /*