ivas_dirac_dec_render_sf_fx cleanup

EVS 26.444 BE test passes.
pytests results: 588 failed, 381 skipped

MLD scores:
Original inputs:
MLD > 10: 112; Out of these, 51 cases are PLC
MLD > 5 : 100
MLD < 5 : 376

+10dB inputs:
MLD > 10: 306
MLD > 5 : 118
MLD < 5 : 164

-10dB inputs:
MLD > 10: 69
MLD > 5 : 63
MLD < 5 : 456