mb/google/kahlee: Enable display backlight control in Windows

Utilize the SOC_AMD_COMMON_BLOCK_GRAPHICS_ATIF to provide the Windows
driver with information on backlight settings.

TEST: Boot google/careena to Win10. Observe display brightness controls
functional after driver loads (immediately with patched driver,
30 minutes with unpatched).

Change-Id: I6792a91f26a5f6e4dc478cdde776ff749f08946f
Signed-off-by: CoolStar <coolstarorganization@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78429
Reviewed-by: Eric Lai <ericllai@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

src/mainboard/google/kahlee/Kconfig

@@ -7,6 +7,7 @@ config BOARD_GOOGLE_BASEBOARD_KAHLEE
 	select AMD_APU_PKG_FT4
 	select ALWAYS_LOAD_OPROM
 	select ALWAYS_RUN_OPROM
+	select SOC_AMD_COMMON_BLOCK_GRAPHICS_ATIF
 	select BOARD_ROMSIZE_KB_16384
 	select DRIVERS_I2C_GENERIC
 	select DRIVERS_I2C_HID