HID: wacom: Correct distance scale for 2nd-gen Intuos devices

Distance values reported by 2nd-gen Intuos tablets are on an inverted
scale (0 == far, 63 == near). We need to change them over to a normal
scale before reporting to userspace or else userspace drivers and
applications can get confused.

Ref: linuxwacom/input-wacom#98
Fixes: eda01da ("HID: wacom: Add four new Intuos devices")
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_wac.c

@@ -846,6 +846,8 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 		y >>= 1;
 		distance >>= 1;
 	}
+	if (features->type == INTUOSHT2)
+		distance = features->distance_max - distance;
 	input_report_abs(input, ABS_X, x);
 	input_report_abs(input, ABS_Y, y);
 	input_report_abs(input, ABS_DISTANCE, distance);