drm: Make DRM_IOCTL_GET_CLIENT return EINVAL when it can't find client #idx.

Fixes the getclient test and dritest -c.
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/char/drm/drm_ioctl.c

@@ -235,17 +235,9 @@ int drm_getclient(struct drm_device *dev, void *data,
 	idx = client->idx;
 	mutex_lock(&dev->struct_mutex);
 
-	if (list_empty(&dev->filelist)) {
-		mutex_unlock(&dev->struct_mutex);
-		return -EINVAL;
-	}
-
 	i = 0;
 	list_for_each_entry(pt, &dev->filelist, lhead) {
-		if (i++ >= idx)
-			break;
-	}
-
+		if (i++ >= idx) {
 			client->auth = pt->authenticated;
 			client->pid = pt->pid;
 			client->uid = pt->uid;
@@ -254,6 +246,11 @@ int drm_getclient(struct drm_device *dev, void *data,
 			mutex_unlock(&dev->struct_mutex);
 
 			return 0;
+		}
+	}
+	mutex_unlock(&dev->struct_mutex);
+
+	return -EINVAL;
 }
 
 /**