Apparently GCC gets bent over comparing enum values against zero.
Replace the conditional with something less readable.
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170921013821.1673-1-jsnow@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>