lemp9: add custom backlight levels

src/mainboard/system76/lemp9/acpi/backlight.asl

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+Scope (GFX0)
+{
+	Name (BRIG, Package (0x12)
+	{
+		100, /* default AC */
+		100, /* default Battery */
+		  6,
+		 12,
+		 19,
+		 25,
+		 31,
+		 38,
+		 44,
+		 50,
+		 56,
+		 62,
+		 69,
+		 75,
+		 81,
+		 88,
+		 94,
+		100,
+	})
+}

src/mainboard/system76/lemp9/dsdt.asl

@@ -19,7 +19,8 @@ DefinitionBlock(
 	{
 		#include <soc/intel/common/block/acpi/acpi/northbridge.asl>
 		#include <soc/intel/cannonlake/acpi/southbridge.asl>
-		#include <drivers/intel/gma/acpi/default_brightness_levels.asl>
+		#include <drivers/intel/gma/acpi/gma.asl>
+		#include "acpi/backlight.asl"
 	}
 
 	#include <southbridge/intel/common/acpi/sleepstates.asl>