Optimization of stereo decode path 32kHz @32kbps
| Function | Old avg wmops | New avg wmops | Improvement |
| hp20_fx_32 | 4.036 | 1.348 | 2.688 |
| ncross_corr_self_fx | 1.936 | 0.944 | 0.992 |
Few more functions of fft, scaling related are updated, but wmops gain is not too changed.