Summary: add ruijie b6510 device

[tim-rj]

- What I did
add support of ruijie b6510 device
- How I did it
add ruijie b6510 platform and device
- How to verify it
compile SONiC bin and run in ruijie b6510 device
- Description for the changelog
add ruijie b6510 device

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

[lgtm-com]

This pull request introduces 68 alerts when merging 5dd89d4 into b6ae12b - view on LGTM.com

new alerts:

• 23 for Unused import
• 10 for Variable defined multiple times
• 6 for Unreachable code
• 6 for 'import *' may pollute namespace
• 5 for Unnecessary pass
• 5 for Testing equality to None
• 5 for Unused local variable
• 3 for Redundant comparison
• 2 for Except block handles 'BaseException'
• 1 for Syntax error
• 1 for Non-iterable used in for loop
• 1 for Use of 'global' at module level

[lguohan]

for new platforms, please submit to master branch first.

[lguohan]

new device needs to go to master first.