inliner: No need to pass FatMethod explicitly
inliner: No need to pass FatMethod explicitly

Summary:
Now that the entries in an IRCode object are exposed publicly, we
don't need to pass the FatMethod as a separate argument to our inliner helper
functions just to get around the visibility restriction.

Reviewed By: emma0303

Differential Revision: D4983278

fbshipit-source-id: b6974327cfd9815ba5fc2b5246e225061430ee6f

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