New FFT initialization functions to make it easier for the linker
to optimize the code size when the library is used as a static
library and can't be rebuilt.
Compilation directives for code size optimizations have been removed.
Solve most of f16 issues. But there are still some remaining
build issues with gcc10q4.
2 functions are reverting to scalar version when build with gcc on M55.
(Since Helium versions of those functions are not building).
Christophe Favergeon