mb/google/brya/var/lisbon: Enable SaGv

Enable SaGv support for lisbon

BUG=b:246657849
TEST=FW_NAME=lisbon emerge-brask coreboot
     pass RMT verification

Signed-off-by: Kevin Chiu <kevin.chiu.17802@gmail.com>
Change-Id: Ic7d3203bfe06973b023a38d1aa3d69cce5c3a60c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69013
Reviewed-by: Ricky Chang <rickytlchang@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>

src/mainboard/google/brya/variants/lisbon/overridetree.cb

@@ -6,6 +6,8 @@ fw_config
 end
 
 chip soc/intel/alderlake
+	register "sagv" = "SaGv_Enabled"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |