Remove use of ArmNN.hpp where it is unnecessary.

Signed-off-by: Matthew Bentham <Matthew.Bentham@arm.com>
Change-Id: I6c90eab1c6bad76d5c7b3bf094998fa4b454bcd1
diff --git a/src/armnnOnnxParser/OnnxParser.cpp b/src/armnnOnnxParser/OnnxParser.cpp
index 42bc427..89be428 100644
--- a/src/armnnOnnxParser/OnnxParser.cpp
+++ b/src/armnnOnnxParser/OnnxParser.cpp
@@ -4,7 +4,7 @@
 //
 #include "OnnxParser.hpp"
 
-#include <armnn/ArmNN.hpp>
+#include <armnn/Descriptors.hpp>
 #include <armnn/Utils.hpp>
 #include <VerificationHelpers.hpp>