soc/intel/jasperlake: Hook up GMA ACPI brightness controls

Add function needed to generate ACPI backlight control SSDT, along with
Kconfig values for accessing the registers.

Tested by adding gfx register on google/magpie. Backlight controls
work on Windows 10 and Linux 6.1.

Change-Id: Iaa9872cd590c3b1298667cc80354ed3efd91c6c8
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74324
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>

src/soc/intel/jasperlake/Kconfig

@@ -219,4 +219,16 @@ config SOC_INTEL_JASPERLAKE_DEBUG_CONSENT
 config PRERAM_CBMEM_CONSOLE_SIZE
 	hex
 	default 0x1400
+
+config INTEL_GMA_BCLV_OFFSET
+	default 0xc8258
+
+config INTEL_GMA_BCLV_WIDTH
+	default 32
+
+config INTEL_GMA_BCLM_OFFSET
+	default 0xc8254
+
+config INTEL_GMA_BCLM_WIDTH
+	default 32
 endif