need update ivas_stereo_dmx_evs_fx()

Basic info

• Float reference:
  • Encoder (float): 2401d81e
  • Decoder (float): 2401d81e
• Fixed point:
  • Encoder (fixed): 8a6654bb
  • Decoder (fixed): 8a6654bb

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