vela: Remove unused serialisation params

 - Removed unused nng parameter

Signed-off-by: Tim Hall <tim.hall@arm.com>
Change-Id: I0bb2eb101a84ea8022c8eb7bcbd86d617e933510
diff --git a/ethosu/vela/npu_serialisation.py b/ethosu/vela/npu_serialisation.py
index 27c46ea..ad4d29c 100644
--- a/ethosu/vela/npu_serialisation.py
+++ b/ethosu/vela/npu_serialisation.py
@@ -57,7 +57,7 @@
     memory_tensor.values[start_addr:end_addr] = values
 
 
-def serialise_npu_subgraph_into_tensors(nng, sg, arch, scratch_tens, scratch_fast_tens, flash_tens):
+def serialise_npu_subgraph_into_tensors(sg, arch, scratch_tens, scratch_fast_tens, flash_tens):
     if sg.placement != PassPlacement.Npu:
         return scratch_tens, scratch_fast_tens, flash_tens
 
@@ -135,7 +135,7 @@
     startup_cps.outputs.insert(0, tens)
 
 
-def rewrite_npu_call_ops(nng, sg, arch):
+def rewrite_npu_call_ops(sg, arch):
     if sg.placement != PassPlacement.Cpu:
         return