anv/fence: Default to not ready

anv/fence: Default to not ready

This is kind-of silly.  We *really* need to do a better job of making sure
all objects have all their default values set.  We probably also want to,
eventually, put everything into the BO (to save memory) and, more
specifically, make the GPU write the "ready" flag.  That way GetFenceStatus
won't ever have to call into the kernel.