mac80211: fix mesh_sta_info_get() reshuffle damage

Before "mac80211: clean up mesh sta allocation warning"
was applied, mesh_sta_info_get() was reshuffled to please
sparse. As a result we neglect to initialize newly created
STAs. Fix this.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>