*Why I did it
The current sonic image bringup failed on Silverstone:
4:56:15.957705 sonic NOTICE swss#orchagent: :- addDecapTunnel: Create overlay loopback router interface oid:6000000000520
*How I did it
Enable bcm switch Tunnel function on Silverstone.
*How to verify it
The new sonic image can bringup OK on Silverstone.