All I did was this:
edit etc/apt/sources.list.d/nvidia-l4t-apt-source.list to point to the 35.1 repo (just change the version to r35.1 in both lines)
sudo apt update
sudo apt dist-upgrade
*****@jetson:~$ cat /etc/apt/sources.list.d/nvidia-l4t-apt-source.list
deb https://repo.download.nvidia.com/jetson/common r35.1 main
deb https://repo.download.nvidia.com/jetson/t210 r35.1 main