Why I did it
To overwrite the default DSCP_TO_TC_MAP for tunnel traffic, the attribute sai_tunnel_support must be set to 1.
Before this change, the attribute is set only on dual-tor platform when remap is enabled.
This PR is to set the attribute on all Arista-7260cx3 devices.
Work item tracking
Microsoft ADO 24785776
How I did it
Update the config.bcm template for Arista-7260cx3 devices.
How to verify it
The change is verified by manually rendering the j2 on a T1 testbed.