Fix CLDepthwiseConvolutionLayer 3x3 QASYMM8

Fix errors when computing tensors with one element only

- Replace Tensor3D with raw pointers so to get rid of offset to first element for NCHW layout
- Add stronger out of bound constraints for NHWC layout
- Set the border size to the input's padding for NHWC
- Fill the strides == 0 with the largest stride, so to avoid accessing empty strides and multiplying by 0

Resolve COMPMID-4088

Change-Id: I751a4e6d7094b3c42306ff7f53af848fd35f19ac
Signed-off-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5024
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Manuel Bottini <manuel.bottini@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/CL/kernels/CLDepthwiseConvolutionLayer3x3NHWCKernel.cpp b/src/core/CL/kernels/CLDepthwiseConvolutionLayer3x3NHWCKernel.cpp
index f553fd1..43c3ff3 100644
--- a/src/core/CL/kernels/CLDepthwiseConvolutionLayer3x3NHWCKernel.cpp
+++ b/src/core/CL/kernels/CLDepthwiseConvolutionLayer3x3NHWCKernel.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020 Arm Limited.
+ * Copyright (c) 2018-2021 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -233,7 +233,7 @@
 
     if(_is_quantized)
     {
-        _border_size = BorderSize(is_stride_1 ? 0 : conv_info.pad_left(), 0, std::max(std::max(conv_info.pad_right(), conv_info.pad_bottom()), conv_info.pad_top()), 0);
+        _border_size = BorderSize(input->info()->padding());
 
         // If QASYMM8 and the 8 bit dot product is available, force _num_planes_processed_per_iteration to 1
         if(is_dot8_supported)