Since commit v3.12.0-rc1~332^2 (FindCUDA/select_compute_arch: Add
support for CUDA as a language, 2018-03-15) this module sets
`CUDA_VERSION` based on `CMAKE_CUDA_COMPILER_VERSION` when the language
is enabled.  Limit it to two components for consistency with the
normal `FindCUDA` documentation and behavior.

Fixes: #18231