[flang][driver] Mark the remaining Flang options as FlangOption

This is a follow-up of https://reviews.llvm.org/D157837 in which I
missed a few Flang options in Options.td. This patch simply updates the
remaining options that are already supported by Flang with the relevant
visibility flag:

Fixes:
  * https://lab.llvm.org/buildbot/#/builders/191/builds/22241