COMPMID-1764 NEON: Implement ArgMax/ArgMin

Change-Id: Ibe23aa90b36ffd8553d1d1c35fada5d300fab829
Reviewed-on: https://review.mlplatform.org/475
Reviewed-by: Isabella Gottardi <isabella.gottardi@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
diff --git a/tests/validation/fixtures/ReduceMeanFixture.h b/tests/validation/fixtures/ReduceMeanFixture.h
index 769d7f6..44bb9fc 100644
--- a/tests/validation/fixtures/ReduceMeanFixture.h
+++ b/tests/validation/fixtures/ReduceMeanFixture.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018 ARM Limited.
+ * Copyright (c) 2018-2019 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -113,7 +113,7 @@
         {
             TensorShape output_shape = i == 0 ? src_shape : out.shape();
             output_shape.set(axis[i], 1);
-            out = reference::reduction_operation<T>(i == 0 ? src : out, output_shape, axis[i], ReductionOperation::MEAN_SUM);
+            out = reference::reduction_operation<T, T>(i == 0 ? src : out, output_shape, axis[i], ReductionOperation::MEAN_SUM);
         }
 
         if(!keep_dims)