MLBEDSW-3771: Updated to TF 2.4 flatbuffer schema

Updated tflite loader and mappings from tensorflow 2.3 to tensorflow 2.4

Signed-off-by: Tim Hall <tim.hall@arm.com>
Change-Id: I55884000ee139baf639bb0377008e0534f72fe94
diff --git a/ethosu/vela/operation.py b/ethosu/vela/operation.py
index 963d9e6..09371b7 100644
--- a/ethosu/vela/operation.py
+++ b/ethosu/vela/operation.py
@@ -145,6 +145,7 @@
     )
     Conv2DBias = OperatorInfo(block_type=NpuBlockType.ConvolutionMxN, indices=IFM_WEIGHTS_BIAS_INDICES)
     Cos = OperatorInfo()
+    Cumsum = OperatorInfo()
     Custom = OperatorInfo()  # Custom 3rd party operator, only used in CPU subgraphs
     CustomNpuOp = OperatorInfo()  # NPU custom operator, only used in CPU subgraphs
     DMA = OperatorInfo()