Verify and possibly fix metadata access for rotateAziEle_DirAC

As a continuation of issue #401 (closed), the metadata access in ivas_dirac_dec for azimuth and elevation rotation in binaural rendering should be verified. It is possible that this access is wrong and does not follow properly the metadata circular buffer system. The code below shows the excerpt and there is a Todo marking this task.

ivas_dirac_dec:2185

/* Todo: This access to azimuth & elevation may use wrong indices as access should probably be based on hDirAC->dirac_read_idx */
rotateAziEle_DirAC( hDirAC->azimuth[index_slot], hDirAC->elevation[index_slot], num_freq_bands, hDirAC->num_freq_bands, p_Rmat );
rotateAziEle_DirAC( hDirAC->azimuth[index_slot], hDirAC->elevation[index_slot], num_freq_bands, hDirAC->num_freq_bands, p_Rmat );