Improve wifi test cases 020*, 030*, 031*, 032*, 033* for WiFiMatFunc suite

- add test description

BUG=chromium-os:32670
TEST=none (doc change only)

Change-Id: If4cb36e34d5f7950c1d624791cc64cd64a9fe389
Reviewed-on: https://gerrit.chromium.org/gerrit/28422
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Tan Gao <tgao@chromium.org>
Tested-by: Tan Gao <tgao@chromium.org>
5 files changed