COMPMID-713: Address failures in OCLGrind for CLDirectConvolution

-Changes way of clamping in the kernel side.
-Fills padding with quantized values

Change-Id: I94d17c341fd637fbb24390722162b551b62d16cb
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/111114
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: BSG Visual Compute Jenkins server to access repositories on http://mpd-gerrit.cambridge.arm.com <bsgcomp@arm.com>
diff --git a/tests/validation/CL/DirectConvolutionLayer.cpp b/tests/validation/CL/DirectConvolutionLayer.cpp
index 08d53d5..e6a196a 100644
--- a/tests/validation/CL/DirectConvolutionLayer.cpp
+++ b/tests/validation/CL/DirectConvolutionLayer.cpp
@@ -196,7 +196,7 @@
 TEST_SUITE(Quantized)
 TEST_SUITE(QASYMM8)
 FIXTURE_DATA_TEST_CASE(Run, CLDirectConvolutionLayerQuantizedFixture<uint8_t>, framework::DatasetMode::ALL, combine(combine(data, framework::dataset::make("DataType", DataType::QASYMM8)),
-                                                                                                                    framework::dataset::make("QuantizationInfo", { QuantizationInfo(2.f / 255, 127) })))
+                                                                                                                    framework::dataset::make("QuantizationInfo", { QuantizationInfo(2.f / 255, 10) })))
 {
     // Validate output
     validate(CLAccessor(_target), _reference, tolerance_qasymm8);