Input: add BTN_TOOL_QUINTTAP for reporting 5 fingers on touchpad

"4-finger scroll" is a gesture supported by some applications and
operating systems.

"Resting thumb" is when a clickpad user rests a finger (e.g., a
thumb), in a "click zone" (typically the bottom of the touchpad) in
anticipation of click+move=select gestures.

Thus, "4-finger scroll + resting thumb" is a 5-finger gesture.
To allow userspace to detect this gesture, we send BTN_TOOL_QUINTTAP.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Acked-by: Chase Douglas <chase.douglas@canonical.com>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index c48c81f..9150ee7 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -117,6 +117,7 @@
 	input_event(dev, EV_KEY, BTN_TOOL_DOUBLETAP, count == 2);
 	input_event(dev, EV_KEY, BTN_TOOL_TRIPLETAP, count == 3);
 	input_event(dev, EV_KEY, BTN_TOOL_QUADTAP, count == 4);
+	input_event(dev, EV_KEY, BTN_TOOL_QUINTTAP, count == 5);
 }
 EXPORT_SYMBOL(input_mt_report_finger_count);