Different bit allocation between fix and floating point for some GSC cases

During fixed-point conversion, it has been observed that for some GSC cases, the bit allocation is sometime different between the float and fixed point decoder. This can lead to interoperability issue between fix and float. (would not cause problem for a fix-fix or float-float link).

To solve the issue, fixed-point code need to be added in the floating point routine to ensure both fixed and floating point allocate bits the same way.

So far, we haven't detected major quality issue other than a waveform change, but decoding a different bit allocation for a same bitstream can lead to undefined behavior.

This issues is related to issue fixed point issue sa4/audio/ivas-basop#802 (closed)