Move bss_conf into the vif struct so that drivers can
access it during ->tx without having to store it in
the private data or similar. No driver updates because
this is only for when they want to start using it.
Signed-off-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>