You don't need an OrgDb package to run kegga(). kegga simply reads annotation from the KEGG website.
However KEGG does not provide annotation for the Trichoderma gamsii species, as you can see from their website:
The closest species is Trichoderma reesei.
So you can't do a KEGG enrichment analysis for Trichoderma gamsii because KEGG pathways don't exist for that species.