gemm: fix typo

codes/gemm/gemm.c

@@ -78,7 +78,7 @@ void calc_error(int ni, int nj,
     double *test = &(C[0][0]);
 
     /* calculate the mean squared error */
-    for (i = 0; i < ni*nj; i++)
+    for (i = 0; i < ni*nj; i++) {
         err += (accurate[i] - test[i])*(accurate[i] - test[i]);
     }
     err /= ni*nj;