mb/google/rex/var/ovis: Enable SaGv

This patch enables SaGv with fixed frequency and gears for Ovis.

Restrict memory speed to 6400 MTS as per board design.

BUG=b:282164577
TEST=Verified the settings on google/ovis using debug FSP logs

Change-Id: Ia9703344a8ae9d2ba44a16c62afab820fd8e2177
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76138
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/rex/variants/baseboard/ovis/devicetree.cb

@@ -39,6 +39,22 @@ chip soc/intel/meteorlake
 	# Enable CNVi BT
 	register "cnvi_bt_core" = "true"
 
+	register "sagv" = "SAGV_ENABLED"
+
+	register "sagv_freq_mhz" = "{
+		[0] = 3200,
+		[1] = 6000,
+		[2] = 6400,
+		[3] = 5600,
+	}"
+
+	register "sagv_gear" = "{
+		[0] = 4,
+		[1] = 4,
+		[2] = 4,
+		[3] = 2,
+	}"
+
 	# Set on-board graphics as primary display
 	register "skip_ext_gfx_scan" = "1"