add nvidia-open driver install option

[kykrueger]

I'd like to be able to install the Nvidia drivers from the Nvidia repo.
let me know what you think.

[kykrueger]

Messed up some of the if statement syntax. I'll fix it later

[Halfwalker]

That's a good idea to have the nvidia-open as an option. Though rather than a whole separate control I think it would be cleaner if integrated into the existing query_nvidia setup. So the selection list in
https://github.com/Halfwalker/ZFS-root/blob/master/ZFS-root.sh#L567-L570

${NVIDIA_LATEST} "Latest ${NVIDIA_LATEST}" OFF \
470    "Legacy 470 driver" OFF \
390    "Legacy 390 driver" OFF \
none   "No Nvidia driver" ON \

becomes

${NVIDIA_LATEST} "Latest ${NVIDIA_LATEST}" OFF \
470    "Legacy 470 driver" OFF \
390    "Legacy 390 driver" OFF \
open   "Use Nvidia open driver" OFF \
none   "No Nvidia driver" ON \

Then it's a matter of checking just the one NVIDIA variable and if it's "open" do the cuda-keyring install etc. Kind of like

if [ "${NVIDIA}" == "open" ] ; then
  # fetch cuda-keyring, apt-get update, install nvidia-open
elif [ "${NVIDIA}" != "none" ] ; then
  # apt-add-repository, apt-get update, install nvidia-driver-${NVIDIA}, etc.
fi

If you would like to redo the PR along these lines I would definitely consider it.