Fix broken link in performance models

This fix fixes broken link in performance models as models repo moved
inception to `models/research/inception`:
`https://github.com/tensorflow/models/tree/master/inception#getting-started`
->
`https://github.com/tensorflow/models/tree/master/research/inception#getting-started`



Signed-off-by: Yong Tang <yong.tang.github@outlook.com>