Reusable implementation of default P4 interpreter

That can be shared among many targets running a program equivalent to
default.p4.

Change-Id: Ic13fc4e416f4ad77f71fbd3202277aac9088b3b1
diff --git a/apps/pi-demo/ecmp/BUCK b/apps/pi-demo/ecmp/BUCK
index ebe97de..7c6a9af 100644
--- a/apps/pi-demo/ecmp/BUCK
+++ b/apps/pi-demo/ecmp/BUCK
@@ -4,6 +4,7 @@
     '//incubator/bmv2/model:onos-incubator-bmv2-model',
     '//apps/pi-demo/common:onos-apps-pi-demo-common',
     '//drivers/default:onos-drivers-default',
+    '//drivers/p4runtime:onos-drivers-p4runtime',
 ]
 
 osgi_jar (