Cover tosa AOT tests in CI (#267)

Summary:
Pull Request resolved: #267

tosa backend tests (python tests) will be added to `backends/tosa/test` dir

Reviewed By: huydhn

Differential Revision: D49169366

fbshipit-source-id: e67433eeabc137e902a888c3abdb77526f8d46e7

Author: guangy10

backends/tosa/test/test_tosa_example.py

@@ -34,3 +34,5 @@ addopts =
     # kernels/
     kernels/prim_ops/test/test_prim_ops.py
     kernels/test/test_case_gen.py
+    # backends/tosa
+    backends/tosa/test