Input: add keycode for performance mode key

Alienware calls this key "Performance Boost". Dell calls it "G-Mode".

The goal is to have a specific keycode to detect when this key is
pressed, so userspace can act upon it and do what have to do, usually
starting the power profile for performance.

Signed-off-by: Marcos Alano <marcoshalano@gmail.com>
Link: https://lore.kernel.org/r/20250509193708.2190586-1-marcoshalano@gmail.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>