[ONCPUML-7] arm_compute support for ND parallelism

Currently 1D ranges of work are specified by the scheduler
via two integers, start and end.  This limit opportunities
for advance parallelism and scheduling

This patch expands the interfaces to allow for ND parallism.

`GemmCommon::get_window_size` now returns an `NDRange` specifying the work
in N-dimensions rather than with the single integer it used prior (1D)

Execute now takes an `NDCoordinate` which specifies an `NDRange` with a start
position for that work along with an `NDCoordinate` to specify the thread location

In addition to expanding the interface to enable this functionality,
we have added the capability to SGEMM when the number of threads is high
this has the effective of allowing a much greater degree of parallelism
where te problem dimension would previously have limited the number of threads.

Change-Id: I3e1a8b7276216627bec4ff6f24ac2147552ea9fb
Signed-off-by: Joseph Dobson <joseph.dobson@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/2962
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/NEON/kernels/arm_gemm/gemv_batched.hpp b/src/core/NEON/kernels/arm_gemm/gemv_batched.hpp
index be2f561..939788e 100644
--- a/src/core/NEON/kernels/arm_gemm/gemv_batched.hpp
+++ b/src/core/NEON/kernels/arm_gemm/gemv_batched.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 ARM Limited.
+ * Copyright (c) 2017-2020 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -58,7 +58,7 @@
         UNUSED(ldc);
     }
 
-    unsigned int get_window_size() const override {
+    ndrange_t get_window_size() const override {
         return _subgemm->get_window_size();
     }
 
@@ -66,8 +66,8 @@
         _subgemm->set_nthreads(nthreads);
     }
 
-    void execute(unsigned int start, unsigned int end, int threadid) override {
-        _subgemm->execute(start, end, threadid);
+    void execute(const ndcoord_t& work_range, const ndcoord_t& thread_locator, int threadid) override {
+        _subgemm->execute(work_range, thread_locator, threadid);
     }
 
     size_t get_working_size() const override {