Bluetooth: SDP: fix sdp record not uninitialized

sdp matching_recs maybe filled with uninitialized record. if
sdp_svc_search_req come from remote with invalid max_rec_count,
which is greater than num_services, matching_recs would response
uninitialized record result.

Signed-off-by: Kai Cheng <chengkai@xiaomi.com>