Previously, trusted (or no-mitigations) has been tested on a subset of builders
from all platforms. This reduces it to arm-sim and native Android devices.

Change-Id: I90066686e6a92db4a944025538e01a117f324421
Reviewed-on: https://chromium-review.googlesource.com/c/1433777Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59062}