mac80211: fix panic when using hardware WEP

e039fa4a ("mac80211: move TX info into
skb->cb") misplaced code for setting hardware WEP keys.  Move it back.
This fixes kernel panic in b43 if WEP is used and hardware encryption
is enabled.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>