IVGCVSW-5783 'Add AsyncExecution Capability'

* Added AsyncExecution to the BackendCapability enum class.
* Logged a warning if backends do not support AsyncExecution capability if AsyncNetwork is created.

Signed-off-by: Sadik Armagan <sadik.armagan@arm.com>
Change-Id: I49f8467297f4b6b8e414cb6a3638a7d3f1bb886a
diff --git a/src/backends/neon/NeonBackend.hpp b/src/backends/neon/NeonBackend.hpp
index 42c6666..34606f9 100644
--- a/src/backends/neon/NeonBackend.hpp
+++ b/src/backends/neon/NeonBackend.hpp
@@ -9,6 +9,10 @@
 namespace armnn
 {
 
+const std::set<armnn::BackendCapability> cpuAccCapabilities {
+    // add new capabilities here..
+};
+
 class NeonBackend : public IBackendInternal
 {
 public:
@@ -47,6 +51,8 @@
 
     IBackendInternal::IBackendSpecificModelContextPtr CreateBackendSpecificModelContext(
         const ModelOptions& modelOptions) const override;
+
+    bool HasCapability(BackendCapability capabilityClass) const override;
 };
 
 } // namespace armnn