Commit 91b8eba9 ("vgabios: remove submodule and build rules.")
removed the vgabios submodule, but left some traces in the configure
script.  Remove them.

Reported-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200622131240.9624-1-kraxel@redhat.com