Rename EstimateTCXNoiseLevel_ivas_fx()

Bug description

The function EstimateTCXNoiseLevel_ivas_fx() should be renamed to EstimateTCXNoiseLevel_fx() and the function header should be aligned.

/*-----------------------------------------------------------*
 * EstimateTCXNoiseLevel()
 *
 * Estimate and quantize noise factor                        *
 *-----------------------------------------------------------*/

static void EstimateTCXNoiseLevel_ivas_fx(
    Encoder_State *st,               /* i  : encoder state handle                            */
    Word32 x_orig[],                 /* i  : shaped MDCT spectrum         Q(31-x_orig_e)     */
    Word16 x_orig_e,                 /* i  : shaped MDCT spectrum exponent                   */
    Word32 spectrum[],               /* i/o: quantized MDCT spectrum                         */
    const Word16 gain_tcx,           /* i  : global gain              Q(15-gain_tcx_e)       */
    const Word16 gain_tcx_e,         /* i  : global gain exponent                            */
    const Word16 L_frame,            /* i  : frame length                                    */
    const Word16 noiseFillingBorder, /* i  : noise filling border                            */
    const Word16 hm_active,          /* i  : flag indicating if the harmonic model is active */
    Word16 *fac_ns,                  /* o  : noise filling level, fac_ns_q                       */
    Word16 *fac_ns_q                 /* o  : quantized noise filling level, Q0               */
)