mac80211: allow vendor specific cipher suites

Allow drivers to specify their own set of cipher
suites to advertise vendor-specific ciphers. The
driver is then required to implement hardware
crypto offload for it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>