RS: number of existing channels on the heap mem wrong

Basic info

Bug description

For the reallocaion of the tc/output channels on the heap a wrong number of existing channels is determined in some RS scenarios (ISM/OMASA/SBA), because the number of channels is calculated using ivas_get_nchan_buffers_dec(), but already with the settings of the new bit rate instead of the old one.

Ways to reproduce

(Clear steps or refer to a failing automated test, e.g. with a pipeline link)