mac80211: fix BSS info reconfiguration

When reconfiguring an interface due to a previous
hardware restart, mac80211 will currently include
the new IBSS flag on non-IBSS interfaces which may
confuse drivers.

Instead of doing the ~0 trick, simply spell out
which things are going to be reconfigured.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>