Adding Bazel BUILD files for yang subsystem.

Change-Id: I957cc95d56eb2ddf6906fa4a396ce2556b9b5e86
diff --git a/tools/build_rules/prelude_bazel b/tools/build_rules/prelude_bazel
index 3c71020..b426887 100644
--- a/tools/build_rules/prelude_bazel
+++ b/tools/build_rules/prelude_bazel
@@ -12,6 +12,7 @@
     "TEST",
     "TEST_ADAPTERS",
     "TEST_REST",
+    "ONOS_YANG",
     "generated_java_libraries",
 )
 load("//tools/build/bazel:osgi_java_library.bzl", "osgi_jar", "osgi_jar_with_tests")