This patch adds mic mute keycode support for the Lenovo Thinkpad USB
keyboard. Support for this keycode was introduced upstream, and will be
defined in upcoming 3.1 Linux Kernel input.h header:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=33009557bd
Signed-off-by: Martin Pitt <martin.pitt@ubuntu.com>