COMPMID-2177 Fix clang warnings

Change-Id: I4beacfd714ee3ed771fd174cce5d8009a2961380
Signed-off-by: Michalis Spyrou <michalis.spyrou@arm.com>
Reviewed-on: https://review.mlplatform.org/c/1065
Reviewed-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/arm_compute/graph/Graph.h b/arm_compute/graph/Graph.h
index 2a77682..878976f 100644
--- a/arm_compute/graph/Graph.h
+++ b/arm_compute/graph/Graph.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018 ARM Limited.
+ * Copyright (c) 2018-2019 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -216,7 +216,7 @@
      *
      * @return Tensor ID
      */
-    TensorID create_tensor(TensorDescriptor desc = TensorDescriptor());
+    TensorID create_tensor(const TensorDescriptor &desc = TensorDescriptor());
 
 private:
     GraphID                              _id      = GraphID(0); /**< Graph id */