autotest: Depend on built in board detection

BUG=None
TEST=WiFi performance tests that use this in perf key making still pass.

Change-Id: I7560b1b76cf38d57c9e8c3609dc5bcbe69041d52
Reviewed-on: https://chromium-review.googlesource.com/173237
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: David James <davidjames@chromium.org>
2 files changed