COMPMID-2819: Adding tolerance of 1 to CLColorConvert RGB8toU8 tests

Both rounding-to-zero and rounding-to-nearest even generate mismatches
with difference of 1 between reference and OpenCL implementation.
Therefore, this patch adds a tolerance to the test.

Change-Id: Id01a04c2b738ba0cc2981b675824cf3a838dc7e9
Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/2737
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/tests/validation/CL/ColorConvert.cpp b/tests/validation/CL/ColorConvert.cpp
index 6bfe67b..d4322fc 100644
--- a/tests/validation/CL/ColorConvert.cpp
+++ b/tests/validation/CL/ColorConvert.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 ARM Limited.
+ * Copyright (c) 2017-2020 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -41,6 +41,7 @@
 namespace
 {
 constexpr AbsoluteTolerance<uint8_t> tolerance_nv(2);
+constexpr AbsoluteTolerance<uint8_t> tolerance_u8(1);
 
 // Input data sets
 const auto RGBDataset  = framework::dataset::make("FormatType", { Format::RGB888, Format::RGBA8888 });
@@ -228,7 +229,7 @@
     // Validate output
     for(unsigned int plane_idx = 0; plane_idx < _dst_num_planes; ++plane_idx)
     {
-        validate(CLAccessor(*_target.cl_plane(plane_idx)), _reference[plane_idx]);
+        validate(CLAccessor(*_target.cl_plane(plane_idx)), _reference[plane_idx], tolerance_u8);
     }
 }
 FIXTURE_DATA_TEST_CASE(RunLarge, CLColorConvertFixture<uint8_t>, framework::DatasetMode::NIGHTLY, combine(datasets::Large2DShapes(), ColorConvert_RGB_to_U8))
@@ -236,7 +237,7 @@
     // Validate output
     for(unsigned int plane_idx = 0; plane_idx < _dst_num_planes; ++plane_idx)
     {
-        validate(CLAccessor(*_target.cl_plane(plane_idx)), _reference[plane_idx]);
+        validate(CLAccessor(*_target.cl_plane(plane_idx)), _reference[plane_idx], tolerance_u8);
     }
 }
 TEST_SUITE_END()