gu605my: enable zeph g16 backlight control

Author: Relief Melone

asus/zephyrus/gu605my/default.nix

@@ -7,6 +7,7 @@
     ../../../common/gpu/nvidia/ada-lovelace
     ../../../common/pc/laptop
     ../../../common/pc/laptop/ssd
+    ../shared/backlight.nix
   ];
 
   hardware.nvidia = {

asus/zephyrus/shared/backlight.nix

@@ -0,0 +1,9 @@
+{ ... }:
+{
+  # These flags are used to enable backlight control when the dGPU is working in hybrid mode
+  boot.kernelParams = [
+    "i915.enable_dpcd_backlight=1"
+    "nvidia.NVreg_EnableBacklightHandler=0"
+    "nvidia.NVReg_RegistryDwords=EnableBrightnessControl=0"
+  ];
+}