cfg80211: allow vendor specific cipher suites

cfg80211 currently rejects all cipher suites it
doesn't know about for key length checking
purposes. This can lead to inconsistencies when
a driver advertises an algorithm that cfg80211
doesn't know about. Remove this rejection so
drivers can specify any algorithm they like.

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>