You can do it with the hammer method:
SElECT * FROM (
SELECT stop_id, stop_name, stop_lat, stop_lon, zone_id
FROM stops WHERE stop_id = 97
) a INNER JOIN (
select st.stop_id, GROUP_CONCAT( distinct rt.route_short_name) as routes
from routes rt, trips tr, stop_times st
where rt.route_id = tr.route_id
and tr.trip_id = st.trip_id
and st.stop_id = 97
) b ON a.stop_id = b.stop_id
or by joining them:
select stops.stop_id,
stops.stop_name,
stops.stop_lat,
stops.stop_lon,
stops.zone_id,
GROUP_CONCAT( distinct rt.route_short_name) as routes
from routes rt, trips tr, stop_times st, stops
where rt.route_id = tr.route_id
and tr.trip_id = st.trip_id
and st.stop_id = stops.stop_id
and st.stop_id = 97
group by st.stop_id