irqbypass: Disallow NULL token

A NULL token is meaningless and can only lead to unintended problems.
Error on registration with a NULL token, ignore de-registrations with
a NULL token.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2 files changed