faft: Refactor the delay constants out to a new class FAFTDelayConstants

This refactoring helps the support of per-platform delay constants. Such
that we can use some short-delay-setting for high-speed devices to reduce
unnecessary waiting time.

BUG=chromium-os:35792
TEST=run_remote_tests.sh --board link --remote dut suite:faft

Change-Id: I1080cb6dcff767b0aef869b0f3c4dbf2a949e923
Reviewed-on: https://gerrit.chromium.org/gerrit/36763
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
8 files changed