Then users can remap the keycode from userspace. If without the remap,
the input device will pass KEY_MICMUTE to userspace, but in X11 layer,
it uses KEY_F20 rather than KEY_MICMUTE for XF86AudioMicMute. After
adding the keycode map, users can remap the keycode to any value users
want.

Cc: <stable@vger.kernel.org>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>