Input: add a driver for TSC-40 serial touchscreen

This patch adds the TSC-40 serial touchscreen driver and should be
compatible with TSC-10 and TSC-25.

The driver was written by Linutronix on behalf of Bachmann electronic GmbH.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/include/linux/serio.h b/include/linux/serio.h
index e26f478..be7dfb0 100644
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -199,5 +199,6 @@
 #define SERIO_DYNAPRO	0x3a
 #define SERIO_HAMPSHIRE	0x3b
 #define SERIO_PS2MULT	0x3c
+#define SERIO_TSC40	0x3d
 
 #endif