Disable test case test_w2l_arm.py::test_w2l_u85_BI

test_w2l_arm.py::test_w2l_u85_BI fails intermittently by timing out.
Disable the test case until we have a solution.

Change-Id: Ib49a85c33fdec7e8d01c82e999be7c9dd80657d8

Author: Martin Lindström

backends/arm/test/models/test_w2l_arm.py

@@ -132,6 +132,7 @@ def test_w2l_u55_BI(self):
     @pytest.mark.slow
     @pytest.mark.corstone_fvp
     @conftest.expectedFailureOnFVP  # TODO: MLETORCH-761
+    @pytest.mark.skip(reason="Intermittent timeout issue: MLETORCH-856")
     def test_w2l_u85_BI(self):
         tester = self._test_w2l_ethos_BI_pipeline(
             self.w2l,