input: Add support for "Do Not Disturb"

HUTRR94 added support for a new usage titled "System Do Not Disturb"
which toggles a system-wide Do Not Disturb setting. This commit simply
adds a new event code for the usage.

Signed-off-by: Aseda Aboagye <aaboagye@chromium.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/Zl-gUHE70s7wCAoB@google.com


Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>