COMPMID-2819: Enable PadLayer on NEON graph backend.

Signed-off-by: Georgios Pinitas <georgios.pinitas@arm.com>
Change-Id: I0114d6999413cbb0602db19c68b9c41c419c6df0
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/2682
Reviewed-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/graph/nodes/PadLayerNode.cpp b/src/graph/nodes/PadLayerNode.cpp
index e7996d2..1bd0776 100644
--- a/src/graph/nodes/PadLayerNode.cpp
+++ b/src/graph/nodes/PadLayerNode.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018 ARM Limited.
+ * Copyright (c) 2018-2020 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -32,7 +32,7 @@
 {
 namespace graph
 {
-PadLayerNode::PadLayerNode(PaddingList &padding)
+PadLayerNode::PadLayerNode(const PaddingList &padding)
     : _padding(padding)
 {
     _input_edges.resize(1, EmptyEdgeID);