drm/nouveau: don't complain for disabled timingset entries

Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_perf.c

@@ -127,6 +127,7 @@ nouveau_perf_timing(struct drm_device *dev, struct bit_entry *P,
 
 	entry += ramcfg * recordlen;
 	if (entry[1] >= pm->memtimings.nr_timing) {
+		if (entry[1] != 0xff)
 			NV_WARN(dev, "timingset %d does not exist\n", entry[1]);
 		return NULL;
 	}