need update ivas_stereo_dmx_evs_fx()
# Basic info
<!--- Add commit SHA used to reproduce-->
- Float reference:
- Encoder (float): 2401d81eadba88ef351691ffba677d7937a84b05
- Decoder (float): 2401d81eadba88ef351691ffba677d7937a84b05
- Fixed point:
- Encoder (fixed): 8a6654bb0ccc82a3db7efa4bf6050b58568f78f2
- Decoder (fixed): 8a6654bb0ccc82a3db7efa4bf6050b58568f78f2
# Bug description
There are some mistakes and none-optimized process in calc_poc_fx()
There are redundant codes of IF() in calc_poc_fx()
# Ways to reproduce
```
./IVAS_cod -stereo_dmx_evs 13200 48 voice_music.wav temp.bs
./IVAS_dec 48 temp.bs out_voice_music.wav
```
<!--Commandline or script-->
```bash
```
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issue