Improve WMOPS of sns_1st_cod_fx()

Basic info

The sns_1st_cod_fx() function internally uses unnecessary BASOP_Util_Add_Mant32Exp() calls. Removing them would improve WMOPS.

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

Bug description

Ways to reproduce

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