Learning mode will learn MAC addresses by creating ALE entries, but packets are dropped rather than forwarded. As the name suggests, to forward packets a port needs to be in forwarding state.
I posted a tested minimal switch setup procedure on the dm814x forum. The am335x should be similar (though beware, for some inexplicable reason various register blocks have been reordered and some control bits have been moved from one register to another).
Keep in mind however that this will not result in a well-behaved standards-compliant switch. Without proper execution of the Spanning Tree Protocol and such, packet loops could occur for example.
Matthijs