Change the header guard around certain numext functions to be CUDA specific.
Change the header guard around certain numext functions to be CUDA specific.

ritsu1228/eigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,ritsu1228/eigen,pasuka/eigen,pasuka/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,ritsu1228/eigen