wifi: mac80211_hwsim: always activate all links

By default, even in client mode, hwsim always had all links
active, where it then uses them in a round-robin fashion.
Re-enable that by activating all valid links work right after
the connection is authorized.

Change-Id: I1e04b12b2784ea52f91f4bffb2c4af7686482435
Signed-off-by: Johannes Berg <johannes.berg@intel.com>