mb/google/skyrim: Enable DmaProperty on WLAN device

Set the DmaProperty in the device's _DSD so that the OS can treat the
device as untrusted.

BUG=b:278310256
TEST=cat /sys/bus/pci/devices/<wifi>/untrusted == 1
     iperf3 -c <iperf3-server> -t 60 (No performance regressions seen)

Change-Id: I06369a19afa5b881b26f5c1eb243e2db41a9bb36
Signed-off-by: Mark Hasemeyer <markhas@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75095
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Van Patten <timvp@google.com>

src/mainboard/google/skyrim/variants/baseboard/devicetree.cb

@@ -94,6 +94,7 @@ chip soc/amd/mendocino
 			chip drivers/pcie/generic
 				register "wake_gpe" = "GEVENT_8"
 				register "wake_deepest" = "ACPI_S0"
+				register "add_acpi_dma_property" = "true"
 				register "name" = ""WLAN""
 				device pci 00.0 on end
 			end