Upgrade ONOS to yang tools version 2.5

Change-Id: I2a8f9ca6637185522023123f8e0b68cbe750d3fd
diff --git a/tools/build/onos-buck b/tools/build/onos-buck
index aa5035d..0a839e0 100755
--- a/tools/build/onos-buck
+++ b/tools/build/onos-buck
@@ -9,7 +9,7 @@
 BUCK_SHA="45d8bd28f441991257babf89f7a317edb3a2b536"
 
 # onos-yang-tools buck plugin version
-YANG_VER="2.4.7"
+YANG_VER="2.5"
 ONOS_PLUGIN_VER="1.0.3"
 MAVEN_BASE="https://repo1.maven.org/maven2"
 MAVEN_ONOSPROJECT="$MAVEN_BASE/org/onosproject"