mac80211: don't validate unchanged AP bandwidth while tracking

The MLME code in mac80211 must track whether or not the AP changed
bandwidth, but if there's no change while tracking it shouldn't do
anything, otherwise regulatory updates can make it impossible to
connect to certain APs if the regulatory database doesn't match the
information from the AP. See the precise scenario described in the
code.

This still leaves some possible problems with CSA or if the AP
actually changed bandwidth, but those cases are less common and
won't completely prevent using it.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=70881



Cc: stable@vger.kernel.org
Reported-and-tested-by: Nate Carlson <kernel@natecarlson.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>