[MLBEDSW-2857] Fix serialisation of non byte tensors

Fixed serialisation of scalar ifm tensors with values larger than
byte sized.

Signed-off-by: Fredrik Svedberg <fredrik.svedberg@arm.com>
Change-Id: I2714398db91b83f24e5271c1d5de1c0e8211f9ab
diff --git a/ethosu/vela/npu_serialisation.py b/ethosu/vela/npu_serialisation.py
index c6b0d87..6277a6d 100644
--- a/ethosu/vela/npu_serialisation.py
+++ b/ethosu/vela/npu_serialisation.py
@@ -52,6 +52,8 @@
 def copy_ifm_values_to_memory_tensor(memory_tensor, src_tensor):
     start_addr = src_tensor.address
     values = src_tensor.quant_values.flatten()
+    if src_tensor.dtype.size_in_bytes() > 1:
+        values = np.frombuffer(values.tobytes(), dtype=np.uint8)
     end_addr = start_addr + values.size
     memory_tensor.values[start_addr:end_addr] = values