mainboard/google/meowth: Enable System Agent dynamic frequency

Enable System Agent dynamic frequency support by default.

BUG=None
TEST=Build and flash with debug version FSP, check SaGv in serial print
to be set to "4".

Change-Id: I7dd29db206b06e600407bb0b1d0bc7530f4ac93e
Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/25093
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/zoombini/variants/meowth/devicetree.cb

@@ -28,7 +28,7 @@ chip soc/intel/cannonlake
 	end
 
 	# FSP configuration
-	register "SaGv" = "3"
+	register "SaGv" = "SaGv_Enabled"
 	register "FspSkipMpInit" = "1"
 	register "SmbusEnable" = "1"
 	register "ScsEmmcEnabled" = "1"