[OE-core] Enabling NEON instructions for fftw

[Philip Balister]

So, recent versions of fftw have NEON support for the single precision
build. In the poast, I just passed --enable-neon to configure or the
armv7a case. Now, this is not entirely correct, since some armv7a's lack
a NEON coprocessor.

Does anyone have a suggestion for how to handle this better? Personally,
I think if you want to run fftwf without NEON, you should have your head
examined, but I would like to avoid generating packages that SIGILL on
people.

Philip