Supported hardware can be found for your architecture starting at
www.openbsd.org/plat.html -- but to discover which drivers allow "Host AP" mode, you'll have to click on each individual driver and read through the man page.
An ethernet connected Acess Point is known as a "Wireless Ethernet Bridge" and there are several makes and models, which you can find with a little bit of Google Fu. As far as the wire-connected host is concerned, WiFi connected devices are just MAC and IP addresses reached by a standard Ethernet NIC.