Stats event from target might have several sub events, and some event
has no peer stats but have adv/ext2 peer stats.
Check ext/ext2 peer stats even no peer stats in
target_if_cp_stats_extract_peer_stats(). Fix copy adv stats size error
in tgt_mc_cp_stats_prepare_n_send_raw_station_stats(). Although
get_station_stats_cb and get_peer_stats_cb is union callbacks,
better to assign to get_station_stats_cb because it is for
TYPE_STATION_STATS.
Change-Id: I0bead0cbb8b549cc538ef4a7327f0a8303c90bd1
CRs-Fixed: 2801842
bb1e3c8933