mb/google/rex: Enable RFIM for CNVi

This patch enables the radio frequency interference mitigation for Rex.

BUG=b:248391777
TEST=Booted to OS on Rex board. Verified RFIM DSM is presented to kernel
through ACPI SSDT.

Change-Id: I22f9861452c2c222dd7a33bfeb02c63b026bf2f7
Signed-off-by: zhaojohn <john.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67791
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

src/mainboard/google/rex/variants/rex0/overridetree.cb

@@ -229,6 +229,7 @@ chip soc/intel/meteorlake
 			chip drivers/wifi/generic
 				register "wake" = "GPE0_PME_B0"
 				register "is_untrusted" = "true"
+				register "enable_cnvi_ddr_rfim" = "true"
 				device generic 0 on end
 			end
 		end