Fix msan uninitialized psEncCtrl->LTP_scale_Q14

The value was never actually used (valgrind didn't complain) but msan
was complaining because it was passed as an argument.

silk/fixed/find_pred_coefs_FIX.c

@@ -118,6 +118,7 @@ void silk_find_pred_coefs_FIX(
         silk_memset( psEncCtrl->LTPCoef_Q14, 0, psEnc->sCmn.nb_subfr * LTP_ORDER * sizeof( opus_int16 ) );
         psEncCtrl->LTPredCodGain_Q7 = 0;
         psEnc->sCmn.sum_log_gain_Q7 = 0;
+        psEncCtrl->LTP_scale_Q14 = 0;
     }
 
     /* Limit on total predictive coding gain */