mac80211: Fix debugfs file add/del for netdev

Previous version was using incorrect union structures for non-AP
interfaces when adding and removing max_ratectrl_rateidx and
force_unicast_rateidx entries. Depending on the vif type, this ended
up in corrupting debugfs entries since the dentries inside different
union structures ended up going being on top of eachother.. As the
end result, debugfs files were being left behind with references to
freed data (instant kernel oops on access) and directories were not
removed properly when unloading mac80211 drivers. This patch fixes
those issues by using only a single union structure based on the vif
type.

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>