CHROMIUM: mac80211: add debugfs to set wmm parameters

This patch adds debugfs support for setting WMM parameters for all
access categories(BE, BK, VI, VO).

BUG=b:131190469
TEST=Tested by writing cwmin and cwmax into debugfs
echo "ac 0 cwmin 15 cwmax 1023 aifs 3 noack 0" > wmm_param

Change-Id: I1729b92fe4554a319a703d5f090e9b2131bcccaf
Signed-off-by: Yingying Tang <yintang@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/1710153


Tested-by: Kan Yan <kyan@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Kan Yan <kyan@chromium.org>