Add support of HwSKU Mellanox-SN2700-C28D8

[andriymoroz-mlnx]

Signed-off-by: Andriy Moroz c_andriym@mellanox.com

- What I did

- How I did it

- How to verify it

1. Installed some latest 201803 image we had
2. Built and installed on switch sonic-device-data_1.0-1_all.deb with the new HwSKU configs on running switch (dpkg -i …)
3. Updated minigraph to match port_config.ini
4. Stopped services and removed syncd container
   (not sure this is really needed, just to make sure it will pick up a new sai prorile)
5. Loaded updated minigraph
6. Test command line sudo sfputil show presence and there is no exception.

Ports were created as expected with the speed according to the schema provided by Qi.

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[qiluo-msft]

Please also cherry-pick to master and all release branch after 201803

[lguohan]

it should be other way around. the PR should be generated against master, then cherry-pick into a release branch.

[lguohan]

please submit pr into master branch.

[andriymoroz-mlnx]

cannot be directly merged from master because in master qos config is a template while in 201803 it is a json
To unify need to merge #2023 to 201803 or I can create a separate PR for master

[lguohan]

@andriymoroz-mlnx , can you mark this as ready for review?