Add p2mp tunnnel details in draft-ietf-teas-yang-te

[oscargdd]

Currently the has to main lists under the tunnels grouping, tunnel (which refers to p2p ) and tunnel-p2mp. So far, what is available for p2mp is simply a name, identifier, description and operational-state.

| +--rw tunnel-p2mp* [name]
| +--rw name string
| +--rw identifier? uint16
| +--rw description? string
| +--ro operational-state? identityref

The p2mp list needs to be completed in a similar way as the p2p tunnel one.

[tsaad-dev]

We concluded that p2mp tunnels can be addressed in a separate document and module.
Removed references to p2mp in c595597