Input: add driver for Penmount serial touchscreens

Signed-off-by: Rick Koch <n1gp@hotmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/include/linux/serio.h b/include/linux/serio.h
index 6348e83..ad546a0 100644
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -217,5 +217,6 @@
 #define SERIO_LKKBD	0x28
 #define SERIO_ELO	0x29
 #define SERIO_MICROTOUCH	0x30
+#define SERIO_PENMOUNT	0x31
 
 #endif