MLBEDSW-839: Code generation using external API

Added external API to generate register command streams.

Existing code generation has been refactored to make
use of this API.

Change-Id: Ibb4c2b167809869f16470b14da24f08a65c82b7b
Signed-off-by: Louis Verhaard <louis.verhaard@arm.com>
diff --git a/ethosu/vela/compiler_driver.py b/ethosu/vela/compiler_driver.py
index e089b70..32eef30 100644
--- a/ethosu/vela/compiler_driver.py
+++ b/ethosu/vela/compiler_driver.py
@@ -292,7 +292,7 @@
             nng, sg, arch, options.verbose_high_level_command_stream
         )
         lut.optimize_high_level_cmd_stream(sg, arch)
-        register_command_stream_generator.generate_register_command_stream(
+        register_command_stream_generator.generate_register_command_stream_for_sg(
             nng, sg, arch, options.verbose_register_command_stream
         )
         scratch_tens, scratch_fast_tens, flash_tens = npu_serialisation.serialise_npu_subgraph_into_tensors(