Add optimization for global pooling in pooling_layer.cl

- Simplify the implementation when the pooling size has the same spatial
  dimensions of the input tensor
- Rework the heuristic for F32/F16
- Add test for validating the global pooling path
- Fix compare_dimensions in validation. The validation fails because we have different
  number of dimensions for NCHW and NHWC (e.g. 1,1,2,1(NCHW) -> 2,1,1,1(NHWC)

Change-Id: Iba680cb30bf2a5d0952265a4cc9794f368549ca5
Signed-off-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5510
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/tests/validation/Validation.h b/tests/validation/Validation.h
index a75562b..f1ce0fe 100644
--- a/tests/validation/Validation.h
+++ b/tests/validation/Validation.h
@@ -159,11 +159,13 @@
     {
         // In case a 1D/2D shape becomes 3D after permutation, the permuted tensor will have two/one dimension(s) more and the first (two) value(s) will be 1
         // clang-format off
-        if((dimensions1.num_dimensions() != dimensions2.num_dimensions()) &&
-           ((dimensions1.num_dimensions() != (dimensions2.num_dimensions() + 1)) || (dimensions1.x() != 1)) &&
-           ((dimensions1.num_dimensions() != (dimensions2.num_dimensions() + 2)) || (dimensions1.x() != 1) || (dimensions1.y() != 1)))
+        const auto max_dims = std::max(dimensions1.num_dimensions(), dimensions2.num_dimensions());
+        for(unsigned int i = 3; i < max_dims; ++i)
         {
-            return false;
+            if(dimensions1[i] != dimensions2[i])
+            {
+                return false;
+            }
         }
         // clang-format on
 
@@ -171,14 +173,6 @@
         {
             return false;
         }
-
-        for(unsigned int i = 3; i < dimensions1.num_dimensions(); ++i)
-        {
-            if(dimensions1[i] != dimensions2[i])
-            {
-                return false;
-            }
-        }
     }
 
     return true;