[MLBEDSW-2335] SoftMax int16

Added graph rewrite of Softmax for int16.

Change-Id: Id7885af6056a23e8b8362fb61ae94283251eb398
Signed-off-by: Fredrik Svedberg <fredrik.svedberg@arm.com>
diff --git a/ethosu/vela/npu_serialisation.py b/ethosu/vela/npu_serialisation.py
index 4b5a888..030503d 100644
--- a/ethosu/vela/npu_serialisation.py
+++ b/ethosu/vela/npu_serialisation.py
@@ -130,6 +130,8 @@
 
                     copy_compressed_values_to_memory_tensor(sg.flash_tensor, ps.scale_tensor)
 
+                if ps.lut_tensor is not None:
+                    copy_ifm_values_to_memory_tensor(sg.flash_tensor, ps.lut_tensor)
                 if ps.ifm_tensor is not None and ps.ifm_tensor.mem_type not in (MemType.Scratch, MemType.Scratch_fast):
                     copy_ifm_values_to_memory_tensor(sg.flash_tensor, ps.ifm_tensor)
                 if ps.ifm2_tensor is not None and (