Input: restore EV_ABS ABS_RESERVED

ABS_RESERVED was added in d9ca1c99 and accidentally removed as part of
ffe0e7cf when the high-resolution scrolling code was removed.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

include/uapi/linux/input-event-codes.h

@@ -752,6 +752,15 @@
 
 #define ABS_MISC		0x28
 
+/*
+ * 0x2e is reserved and should not be used in input drivers.
+ * It was used by HID as ABS_MISC+6 and userspace needs to detect if
+ * the next ABS_* event is correct or is just ABS_MISC + n.
+ * We define here ABS_RESERVED so userspace can rely on it and detect
+ * the situation described above.
+ */
+#define ABS_RESERVED		0x2e
+
 #define ABS_MT_SLOT		0x2f	/* MT slot being modified */
 #define ABS_MT_TOUCH_MAJOR	0x30	/* Major axis of touching ellipse */
 #define ABS_MT_TOUCH_MINOR	0x31	/* Minor axis (omit if circular) */