mb/google/karis: Add FW_CONFIG and device for VPU

BUG=b:333605309
TEST=set and unset bit20 in HW_CONFIG and check if VPU(0b.0)
is enabled when bit20 is set, and disabled when cleared.

Change-Id: I6e2230715d783ea7108d71699fd19684ce19e2ff
Signed-off-by: Jamie Ryu <jamie.m.ryu@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81655
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/mainboard/google/rex/variants/karis/overridetree.cb

@@ -34,6 +34,10 @@ fw_config
 		option DISABLE			0
 		option ENABLE			1
 	end
+	field VPU 22
+		option VPU_DIS			0
+		option VPU_EN			1
+	end
 end
 
 chip soc/intel/meteorlake
@@ -581,5 +585,8 @@ chip soc/intel/meteorlake
 			end
 		end
 		device ref hda on end
+		device ref vpu on
+			probe VPU VPU_EN
+		end
 	end
 end