The QEMU_VFIO_DEBUG definition is only modifiable at build-time.
Trace events can be enabled at run-time. As we prefer the latter,
convert qemu_vfio_dump_mappings() to use trace events instead
of fprintf().

Reviewed-by: Fam Zheng <fam@euphon.net>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20201103020733.2303148-7-philmd@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>