mb/google/nissa: Mark CNVi wifi device as untrusted

BUG=b:238937091
TEST=Dump the SSDT on nivviks and check that the wifi device has the
DmaProperty.

Change-Id: I910b7da7050f9aebfe0eb58552c82b1b29de3772
Signed-off-by: Reka Norman <rekanorman@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67044
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kangheui Won <khwon@chromium.org>

src/mainboard/google/brya/variants/baseboard/nissa/devicetree.cb

@@ -157,6 +157,7 @@ chip soc/intel/alderlake
 		device ref cnvi_wifi on
 			chip drivers/wifi/generic
 				register "wake" = "GPE0_PME_B0"
+				register "is_untrusted" = "true"
 				device generic 0 on end
 			end
 		end