Add tetheroffload VTS to general-tests

Also add it to TEST_MAPPING so it's run in presubmits.

Test: na
Bug: 205762647
Change-Id: I9c43ffcff5ccf0fcabcab08101ebc454c7fe3317
diff --git a/tetheroffload/aidl/TEST_MAPPING b/tetheroffload/aidl/TEST_MAPPING
new file mode 100644
index 0000000..c6d4c07
--- /dev/null
+++ b/tetheroffload/aidl/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit" : [
+    {
+      "name": "VtsHalTetheroffloadTargetTest"
+    }
+  ]
+}