Add KEY_MICMUTE and enable it on Lenovo X220

I suspect that this works on T410.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
diff --git a/include/linux/input.h b/include/linux/input.h
index 068784e..a637e78 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -438,6 +438,8 @@
 #define KEY_WIMAX		246
 #define KEY_RFKILL		247	/* Key that controls all radios */
 
+#define KEY_MICMUTE		248	/* Mute / unmute the microphone */
+
 /* Code 255 is reserved for special needs of AT keyboard driver */
 
 #define BTN_MISC		0x100