FFTW: NEON SIMD is float-only (#26321)
FFTW: NEON SIMD is float-only (#26321)

Fix on Apple Mac M1 (aarch64):
```
configure: error: NEON requires single precision
```
LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack