[non-BE] fix for issue 952 : Differences between 5ms and 20ms rendering for ParamUpmix

• Related issues:
• Requested reviewers: @schug , @plains , @bayers , @paulusj

Reason why this change is needed

• With the limiter disabled, rendering to 5ms and to 20ms is not BE for ParamUpmix

Description of the change

• Moved setting of param MC alpha and beta parameters from rendering function to decoding function

Affected operating points

• MC 7_1_4 at 160 kbps
• Bitstream BE
• Decoded output non-BE for 5ms framing
• Decoded output BE for 20ms framing