No cmake variable to explicitly enable/disable documentation

[teonnik]

Currently documentation in rocm_smi/CMakeLists.txt is generated when doxygen and latex are found. However, being able to disable document generation explicitly is still desirable. In particular, I have encountered a problem where the document generation causes my build to hang. This is the case with the package manager spack where I have opened a PR with a patch commenting-out that part of the code. https://github.com/spack/spack/pull/28842

It will be great if an a CMake variable explicitly enabling/disabling documentation is added.