IVGCVSW-3526 Add layer norm support for lstm serialization

* Adds layer norm support for serialization/deserialization
* Adds related unit tests

Change-Id: If80b668accc8b0754a93d18ab3a243284cb383d1
Signed-off-by: Jan Eilers <jan.eilers@arm.com>
diff --git a/src/armnnSerializer/ArmnnSchema.fbs b/src/armnnSerializer/ArmnnSchema.fbs
index e3953df..0fd8da7 100644
--- a/src/armnnSerializer/ArmnnSchema.fbs
+++ b/src/armnnSerializer/ArmnnSchema.fbs
@@ -537,6 +537,11 @@
 
     cellToForgetWeights:ConstTensor;
     cellToOutputWeights:ConstTensor;
+
+    inputLayerNormWeights:ConstTensor;
+    forgetLayerNormWeights:ConstTensor;
+    cellLayerNormWeights:ConstTensor;
+    outputLayerNormWeights:ConstTensor;
 }
 
 table LstmDescriptor {
@@ -546,6 +551,7 @@
     cifgEnabled:bool = true;
     peepholeEnabled:bool = false;
     projectionEnabled:bool = false;
+    layerNormEnabled:bool = false;
 }
 
 table LstmLayer {