nl80211: rework {sched_,}scan event related functions

A couple of functions used with scan events were named with
term "send" although they were only preparing the the event
message so renamed those.

Also remove nl80211_send_sched_scan_results() in favor of
just calling nl80211_send_sched_scan() with the right value.

Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
[mention nl80211_send_sched_scan_results() in the commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>