am 1577e629: am 12006013: fixedfft: Only includes cpu-features.h when __arm__ is defined.

Merge commit '1577e629866b2700e31c9467478e05ebffcc69a1'

* commit '1577e629866b2700e31c9467478e05ebffcc69a1':
  fixedfft: Only includes cpu-features.h when __arm__ is defined.