OSBA to stereo rendering issue

This is a spin-off from !1187 (merged).

The decoding of OSBA in ISM_SBA_MODE_DISC mode has an issue when mixing the ISM rendered part and SBA rendered path, e.g.

stvOSBA_1ISM_2OA48c_OSBA_ISM1_HOA2_b256_wb_cbr_jbm_dly_error_profile_10_dat.dec.stereo.wav

It seems that some code around ivas_ism_render() from ivas_dec() was not brought around to ivas_ism_render_sf() from ivas_jbm_dec_render().