Converted few functions in dec_tcx.

[x] Few functions in dec_tcx converted to fixed point.
[x] Changes made in dependent functions to call the converted functions.

Pytests:
573 failed, 381 skipped and 1 passed for original inputs, +10dB scaled and -10dB scaled inputs.

MLD:
Original: 4 cases > 5
8.622747 9.196089 12.937471 22.589209

+10dB: 13 cases > 5
5.665263 5.665263 6.416382 7.0239 10.756404 10.756404 14.899035 16.60401 16.975687 23.380836 23.678728 27.051519 51.933289

-10dB: 3 cases > 5
8.665655 15.849977 25.000893

MLD deviation issue to be debugged.