IVGCVSW-5636 'Implement NNAPI caching functions'

* Get number of inputs and outputs from optimized network.
* Get number of cached files if backend supports caching.

Signed-off-by: Sadik Armagan <sadik.armagan@arm.com>
Change-Id: Ie02ac123bb7df9b0593a2fe46b5bb564a5994780
diff --git a/src/backends/cl/ClBackend.hpp b/src/backends/cl/ClBackend.hpp
index e0708d1..ffce800 100644
--- a/src/backends/cl/ClBackend.hpp
+++ b/src/backends/cl/ClBackend.hpp
@@ -105,6 +105,8 @@
         return m_UsingCustomAllocator;
     }
 
+    virtual unsigned int GetNumberOfCacheFiles() const override { return 1; }
+
     // Cl requires a arm_compute::IAllocator we wrap the Arm NN ICustomAllocator to achieve this
     class ClBackendCustomAllocatorWrapper : public arm_compute::IAllocator
     {