nl80211: advertise device AP SME

Add the ability to advertise that the device contains the AP SME and
what features it can support.There are currently no features in the
bitmap -- probe response offload will be advertised by a few patches
Arik is working on now (who took over from Guy Eilam) and a device
with AP SME will typically implement and require response offload.

Change-Id: Ic8d75e4933d795d43a0c30df6ec187f4d0ab6d8c
Signed-off-by: Deepthi Gowri <deepthi@codeaurora.org>