IVGCVSW-4170 Also convert constants to FP16 when model converted

Change-Id: Ideeec890a91379bfd52774633b1b35fa1b14f434
Signed-off-by: Derek Lamberti <derek.lamberti@arm.com>
diff --git a/src/armnn/Network.cpp b/src/armnn/Network.cpp
index d164759..53e28c3 100644
--- a/src/armnn/Network.cpp
+++ b/src/armnn/Network.cpp
@@ -842,6 +842,7 @@
     if (options.m_ReduceFp32ToFp16)
     {
         Optimizer::Pass(optGraph, MakeOptimizations(Fp32NetworkToFp16Converter()));
+        Optimizer::Pass(optGraph, MakeOptimizations(ConvertConstantsFloatToHalf()));
     }
 
     // Initialize backend settings