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>

Author: mhalano

include/uapi/linux/input-event-codes.h

@@ -765,6 +765,9 @@
 #define KEY_KBD_LCD_MENU4		0x2bb
 #define KEY_KBD_LCD_MENU5		0x2bc
 
+/* Performance Boost key (Alienware)/G-Mode key (Dell) */
+#define KEY_PERFORMANCE			0x2bd
+
 #define BTN_TRIGGER_HAPPY		0x2c0
 #define BTN_TRIGGER_HAPPY1		0x2c0
 #define BTN_TRIGGER_HAPPY2		0x2c1