Review usage of cx_e and cx_next_band_e in ivas_param_mc_dec_prepare_renderer()

Bug description

The usage of the exponents cx_e and cx_next_band_e in ivas_param_mc_dec_prepare_renderer() are at least confusing, for example in this code:

IF( hParamMC->hMetadataPMC->bAttackPresent && ( EQ_32( hParamMC->synthesis_conf, PARAM_MC_SYNTH_LS_CONV_COV ) || EQ_32( hParamMC->synthesis_conf, PARAM_MC_SYNTH_MONO_STEREO ) ) )
{
    Word16 len = imult1616( nchan_transport, nchan_transport );
    Word16 sc = s_min( getScaleFactor32( cx_fx, len ), getScaleFactor32( cx_next_band_fx, len ) );
    IF( EQ_16( sc, 0 ) )
    {
        Scale_sig32( cx_fx, len, -Q1 );           // add one bit head room
        Scale_sig32( cx_next_band_fx, len, -Q1 ); // add one bit head room
        cx_e = add( cx_e, Q1 );
        cx_next_band_e = add( cx_e, Q1 );
     }
     v_add_fx( cx_fx, cx_next_band_fx, cx_fx, len );
     Copy32( cx_fx, cx_next_band_fx, len );
}

One should think that the line

cx_next_band_e = add( cx_e, Q1 );

should actually read

cx_next_band_e = add( cx_next_band_e, Q1 );

This should be checked.