[webapi] Update spec.json for gamepad

- change messaging to gamepad

Impacted TCs (approved): New 0, Update 0, Delete 0
Unit test Platform: Android
Android test result summary: Pass 0, Fail 0, Blocked 0
Merge pull request #303 from JianfengXu/xujf/gamepad/mainfast

[webapi] Update spec.json for gamepad