ivshmem: Compile debug prints unconditionally to prevent bit-rot

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-13-git-send-email-armbru@redhat.com>
