[OpenBLAS]: benchmark error of potrf

[description]: when the matrix size goes higher than 5800 during the cpotrf test, error info, such as "Potrf info = 5679", will be returned on ARM64 and x86 machines. Uplo = L & F.
[solution]: changed the func for building the matrix so that the complex Hermitian matrix can stay positive definite during the computation.
[dts]:

benchmark/potrf.c

@@ -193,14 +193,14 @@ int main(int argc, char *argv[]){
 	  a[((long)j + (long)j * (long)m) * 2 + 1] = 0.;
 
 	  for(i = j + 1; i < m; i++) {
-	    a[((long)i + (long)j * (long)m) * 2 + 0] = ((double) rand() / (double) RAND_MAX) - 0.5;
+	    a[((long)i + (long)j * (long)m) * 2 + 0] = 0;
 	    a[((long)i + (long)j * (long)m) * 2 + 1] = ((double) rand() / (double) RAND_MAX) - 0.5;
 	  }
 	}
       } else {
 	for (j = 0; j < m; j++) {
 	  for(i = 0; i < j; i++) {
-	    a[((long)i + (long)j * (long)m) * 2 + 0] = ((double) rand() / (double) RAND_MAX) - 0.5;
+	    a[((long)i + (long)j * (long)m) * 2 + 0] = 0.;
 	    a[((long)i + (long)j * (long)m) * 2 + 1] = ((double) rand() / (double) RAND_MAX) - 0.5;
 	  }