Wrong multiplication function used in printing external renderer framesize
# Basic info
<!--- Add commit SHA used to reproduce-->
- Fixed point:
- Renderer (fixed): 244017a12cc5523b6996129d277af1da64c82dc0
# Bug description
The printout of the framesize is always 0ms due to an incorrect computation.
# Ways to reproduce
Run the external renderer with any BINAURAL output configuration variant. Frame size can be unset or set to 5/10/20ms.
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