drm/nouveau: fix acpi edid retrieval

Commit c0077061

 accidentally inverted the logic for nouveau_acpi_edid,
causing it to only show a connector as connected when the edid could not
be retrieved with acpi.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>