MLBEDSW-6425: Update to TensorFlow 2.8 (bugfix)

Generate flatbuffer files with relative imports.

Signed-off-by: Rickard Bolin <rickard.bolin@arm.com>
Change-Id: Idd59bb2ebb829bc42677920577c1f8a04e23ca68
diff --git a/ethosu/vela/tflite/SubGraph.py b/ethosu/vela/tflite/SubGraph.py
index d93c5b5..7cd97f2 100644
--- a/ethosu/vela/tflite/SubGraph.py
+++ b/ethosu/vela/tflite/SubGraph.py
@@ -35,7 +35,7 @@
             x = self._tab.Vector(o)
             x += flatbuffers.number_types.UOffsetTFlags.py_type(j) * 4
             x = self._tab.Indirect(x)
-            from tflite.Tensor import Tensor
+            from .Tensor import Tensor
             obj = Tensor()
             obj.Init(self._tab.Bytes, x)
             return obj
@@ -114,7 +114,7 @@
             x = self._tab.Vector(o)
             x += flatbuffers.number_types.UOffsetTFlags.py_type(j) * 4
             x = self._tab.Indirect(x)
-            from tflite.Operator import Operator
+            from .Operator import Operator
             obj = Operator()
             obj.Init(self._tab.Bytes, x)
             return obj