drm/nouveau: fix oops if i2c bus not found in nouveau_i2c_identify()

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

drivers/gpu/drm/nouveau/nouveau_i2c.c

@@ -333,7 +333,7 @@ nouveau_i2c_identify(struct drm_device *dev, const char *what,
 
 	NV_DEBUG(dev, "Probing %ss on I2C bus: %d\n", what, index);
 
-	for (i = 0; info[i].addr; i++) {
+	for (i = 0; i2c && info[i].addr; i++) {
 		if (nouveau_probe_i2c_addr(i2c, info[i].addr) &&
 		    (!match || match(i2c, &info[i]))) {
 			NV_INFO(dev, "Detected %s: %s\n", what, info[i].type);