Input: allocate keycode for Display refresh rate toggle

Newer Lenovo Yogas and Legions with 60Hz/90Hz displays send a wmi event
when Fn + R is pressed. This is intended for use to switch between the
two refresh rates.

Allocate a new KEY_REFRESH_RATE_TOGGLE keycode for it.

Signed-off-by: Gergo Koteles <soyer@irl.hu>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/15a5d08c84cf4d7b820de34ebbcf8ae2502fb3ca.1710065750.git.soyer@irl.hu


Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>