dt-bindings: leds: Add LED_FUNCTION_FNLOCK

Newer laptops have FnLock LED.

Add a define for this very common function.
Signed-off-by: Gergo Koteles <soyer@irl.hu>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Lee Jones <lee@kernel.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/8ac95e85a53dc0b8cce1e27fc1cab6d19221543b.1712063200.git.soyer@irl.huSigned-off-by: Hans de Goede <hdegoede@redhat.com>

include/dt-bindings/leds/common.h

@@ -46,6 +46,7 @@
 #define LED_FUNCTION_CAPSLOCK "capslock"
 #define LED_FUNCTION_SCROLLLOCK "scrolllock"
 #define LED_FUNCTION_NUMLOCK "numlock"
+#define LED_FUNCTION_FNLOCK "fnlock"
 /*   Obsolete equivalents: "tpacpi::thinklight" (IBM/Lenovo Thinkpads),
      "lp5523:kb{1,2,3,4,5,6}" (Nokia N900) */
 #define LED_FUNCTION_KBD_BACKLIGHT "kbd_backlight"