There are many websites / databases offering an "overview"
of motorbike- friendly accommodation, see
IMHO this should be an option (tag) in OSM for :
tourism=camp_site / tourism=hotel / tourism=hostel / tourism=motel / tourism=guest_house
So the motorbike tourists could download the respective items via Overpass
as GPX POIs (by filtering "tourism=camp_site and motorcycle_friendly=yes" in example)