mac80211: work around broken APs not including HT info

There are some APs, notably 2G/3G/4G Wifi routers, specifically the
"Onda PN51T", "Vodafone PocketWiFi 2", "ZTE MF60" and a similar
T-Mobile branded device [1] that erroneously don't include all the
needed information in (re)association response frames. Work around
this by assuming the information is the same as it was in the
beacon or probe response and using the data from there instead.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=58881.

[1] https://bbs.archlinux.org/viewtopic.php?pid=1277305



Note that this requires marking the first ieee802_11_parse_elems()
argument const, otherwise we'd get a compiler warning.

Cc: stable@vger.kernel.org
Reported-and-tested-by: Michal Zajac <manwe@manwe.pl>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>