harmonization of the 0 bit bwe between EVS and IVAS

Basic info

• Float reference:
  • Encoder (float):
  • Decoder (float):
• Fixed point:
  • Encoder (fixed): a0051869
  • Decoder (fixed):

Bug description

This will include hf_synth_ivas_fx, hf_synthesis_ivas_fx. Part of hf_synth_ivas_fx() will be preserved as it prevent saturation, which also means hp400_12k8_ivas_fx will be preserved too.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-xxxx