COMPMID-2451: Use kernel lws_hint() on enqueue

Avoid querying device's default lws on kernel enqueue as this is already
cached in the kernel during configuration.

Change-Id: Ia26ecb712caeb8f042356815e0cfd23522764d27
Signed-off-by: Georgios Pinitas <georgios.pinitas@arm.com>
Reviewed-on: https://review.mlplatform.org/c/1803
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/CL/kernels/CLChannelExtractKernel.cpp b/src/core/CL/kernels/CLChannelExtractKernel.cpp
index 8bddba8..d2a0f98 100644
--- a/src/core/CL/kernels/CLChannelExtractKernel.cpp
+++ b/src/core/CL/kernels/CLChannelExtractKernel.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2018 ARM Limited.
+ * Copyright (c) 2016-2019 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -181,7 +181,7 @@
         unsigned int idx = 0;
         add_2D_tensor_argument(idx, _input, slice);
         add_2D_tensor_argument(idx, _output, win_sub);
-        enqueue(queue, *this, slice);
+        enqueue(queue, *this, slice, lws_hint());
     }
     while(window.slide_window_slice_2D(slice));
 }