platform/x86: ideapad-laptop: support Fn+R dual-function key

According to the manual, Fn+R adjusts the display refresh rate.
Map Fn+R to KEY_DISPLAYTOGGLE.

Signed-off-by: Gergo Koteles <soyer@irl.hu>
Link: https://lore.kernel.org/r/0cdbc0e6eb65e160384ae0ed152e7de3ded1d9d5.1707604991.git.soyer@irl.hu


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