COMPMID-424 Clean up validation tests for 2D spatial filter functions

* Remove shape_to_valid_region_undefined_border
* Remove hardcoded border size

Change-Id: I3c64148d8f7ce7e960f21d88d3af43bb23501683
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/79106
Reviewed-by: Moritz Pflanzer <moritz.pflanzer@arm.com>
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/tests/validation/TensorOperations.h b/tests/validation/TensorOperations.h
index 843c52f..5557cfc 100644
--- a/tests/validation/TensorOperations.h
+++ b/tests/validation/TensorOperations.h
@@ -716,7 +716,7 @@
 void non_linear_filter(const Tensor<T> &in, Tensor<T> &out, NonLinearFilterFunction function, unsigned int mask_size,
                        MatrixPattern pattern, const uint8_t *mask, BorderMode border_mode, uint8_t constant_border_value)
 {
-    ARM_COMPUTE_ERROR_ON(MatrixPattern::OTHER == pattern && nullptr == mask);
+    ARM_COMPUTE_ERROR_ON(pattern == MatrixPattern::OTHER && mask == nullptr);
 
     using intermediate_type = typename common_promoted_signed_type<T>::intermediate_type;
 
@@ -725,11 +725,7 @@
     std::vector<intermediate_type> vals(sq_mask_size);
     intermediate_type              current_value = 0;
 
-    ValidRegion valid_region = shape_to_valid_region(in.shape());
-    if(border_mode == BorderMode::UNDEFINED)
-    {
-        valid_region = shape_to_valid_region_undefined_border(in.shape(), BorderSize(half_mask_size));
-    }
+    const ValidRegion valid_region = shape_to_valid_region(in.shape(), border_mode == BorderMode::UNDEFINED, BorderSize(half_mask_size));
 
     for(int element_idx = 0, count = 0, index = 0; element_idx < in.num_elements(); ++element_idx, count = 0, index = 0)
     {