mb/google/sarien: Add ACPI brighness controls

Add display panel info and ACPI includes to enable display backlight
control under Windows and MacOS.

TEST=build/boot Win11 on sarien, verify brightness controls functional.

Change-Id: Ic0595c8c977f1203424ab9d91343b8e98414f594
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86907
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/sarien/Kconfig

@@ -4,6 +4,7 @@ config BOARD_GOOGLE_BASEBOARD_SARIEN
 	def_bool n
 	select BOARD_ROMSIZE_KB_32768
 	select DRIVERS_GENERIC_BH720
+	select DRIVERS_GFX_GENERIC
 	select DRIVERS_I2C_GENERIC
 	select DRIVERS_I2C_HID
 	select DRIVERS_SPI_ACPI

src/mainboard/google/sarien/dsdt.asl

@@ -22,6 +22,7 @@ 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>
 		}
 		/* Per board variant mainboard hooks. */
 		#include <variant/acpi/mainboard.asl>

src/mainboard/google/sarien/variants/sarien/devicetree.cb

@@ -214,7 +214,14 @@ chip soc/intel/cannonlake
 	register "gpio_pm[COMM_4]" = "MISCCFG_GPIO_PM_CONFIG_BITS"
 
 	device domain 0 on
-		device ref igpu on  end
+		device ref igpu on
+			chip drivers/gfx/generic
+				register "device_count" = "1"
+				register "device[0].name" = ""LCD0""
+				register "device[0].type" = "panel"
+				device generic 0 on end
+			end
+		end
 		device ref dptf on  end
 		device ref thermal on  end
 		device ref xhci on