std::mutex and std::unique_lock are used in v4l2 directory, mixing Mutex and MutexLocker. This consolidates them to Mutex and MutexLocker. This also fixes vidioc_dqbuf argument to take Mutex instead of MutexLocker. Signed-off-by: Hirokazu Honda <hiroh@chromium.org> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Umang Jain <umang.jain@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>