message: suppress unreachable code warning
  - fix the define condition based on the comment
diff: @@ -4582,6 +4582,7 @@ cvtScaleHalf_<float, short>( const float* src, size_t sstep, short* dst, size_t
  {
  CV_CPU_CALL_FP16(cvtScaleHalf_SIMD32f16f, (src, sstep, dst, dstep, size));
  +#if !defined(CV_CPU_COMPILE_FP16)
  sstep /= sizeof(src[0]);
  dstep /= sizeof(dst[0]);
  @@ -4592,6 +4593,7 @@ cvtScaleHalf_<float, short>( const float* src, size_t sstep, short* dst, size_t
  dst[x] = convertFp16SW(src[x]);
  }
  }
  +#endif
  }
  template<> void
  @@ -4599,6 +4601,7 @@ cvtScaleHalf_<short, float>( const short* src, size_t sstep, float* dst, size_t
  {
  CV_CPU_CALL_FP16(cvtScaleHalf_SIMD16f32f, (src, sstep, dst, dstep, size));
  +#if !defined(CV_CPU_COMPILE_FP16)
  sstep /= sizeof(src[0]);
  dstep /= sizeof(dst[0]);
  @@ -4609,6 +4612,7 @@ cvtScaleHalf_<short, float>( const short* src, size_t sstep, float* dst, size_t
  dst[x] = convertFp16SW(src[x]);
  }
  }
  +#endif
  }
  #ifdef HAVE_OPENVX
  