hostapd: Allow coexistance of HT BSSes with WEP/TKIP BSSes

hostapd: Allow coexistance of HT BSSes with WEP/TKIP BSSes

In multi BSS setups it wasn't possible to set up an HT BSS in
conjunction with a WEP/TKIP BSS. HT needed to be turned off entirely
to allow WEP/TKIP BSSes to be used.

In order to allow HT BSSes to coexist with non-HT WEP/TKIP BSSes add a
new BSS conf attribute "disable_11n" which disables HT capabilities on a
single BSS by suppressing HT IEs in the beacon and probe response
frames. Furthermore, mark all STAs associated to a WEP/TKIP BSS as
non-HT STAs. The disable_11n parameter is used internally; no new entry
is parsed from hostapd.conf.

This allows a non-HT WEP/TKIP BSS to coexist with a HT BSS without
having to disable HT mode entirely. Nevertheless, all STAs associated to
the WEP/TKIP BSS will only be served as if they were non-HT STAs.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>