mac80211: fix nested rtnl locking on ieee80211_reconfig

ieee80211_reconfig already holds rtnl, so calling
cfg80211_sched_scan_stopped results in deadlock.

Use the rtnl-version of this function instead.

Fixes: d43c6b6e ("mac80211: reschedule sched scan after HW restart")
Cc: stable@vger.kernel.org (3.14+)
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>