tools: enable linting for v8_prof_processor.js

`lib/internal/v8_prof_processor.js` was being excluded from linting, but
the only lint issue it has is that it cannot run in strict mode. Disable
the `strict` rule with a comment and remove the file from
`.eslintignore`.

PR-URL: https://github.com/nodejs/node/pull/6262


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Klauke <romaaan.git@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>