mac80211: introduce IEEE80211_HW_TEARDOWN_AGGR_ON_BAR_FAIL

mac80211: introduce IEEE80211_HW_TEARDOWN_AGGR_ON_BAR_FAIL

Commit 1fc08d8b41820ae9059df7871aefca3c0791cf25 "mac80211: retry sending
failed BAR frames later instead of tearing down aggr" caused regression
on rt2x00 hardware (connection hangs). This regression was fixed by
commit a0ed0da1ad4bb38050cfdf4aca5d56767666dfc "rt2x00: Don't let
mac80211 send a BAR when an AMPDU subframe fails". But the latter
commit caused yet another problem reported in
https://bugzilla.kernel.org/show_bug.cgi?id=42828#c22

After long discussion in this thread:
http://mid.gmane.org/20121018075615.GA18212@redhat.com
and testing various alternative solutions, which failed on one or other
setup, we have no other good fix for the issues like just revert both
mentioned earlier commits.

To do not affect other hardware which benefit from commit
1fc08d8b41820ae9059df7871aefca3c0791cf25, instead of reverting it,
introduce flag that when used will restore mac80211 behaviour before
the commit.

Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
[replaced link with mid.gmane.org that has message-id]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>