fftw: change default value of simd variant for other than x86_64 (#11627)
fftw: change default value of simd variant for other than x86_64 (#11627)

* Use spec.architecture.target insted of platform.

* remove default in simd variant value.
simd variant change to archtecture independent values.

* Add check simd values.

* rewrite check simd values.

* * flake8
* change aarch64 to arm (neon support only 32 bit arm.)

iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack