mac80211: introduce IEEE80211_HW_TEARDOWN_AGGR_ON_BAR_FAIL

mac80211: introduce IEEE80211_HW_TEARDOWN_AGGR_ON_BAR_FAIL

Commit 67890b65c9f2062be14975cf2159e0fcb8c7c0f3 "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 faf8e418d0e6fbae4d3797bced5956547c2a93c "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
67890b65c9f2062be14975cf2159e0fcb8c7c0f3, 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>