[NFC][InlineCost] Simplify internal inlining cost interface

Summary:
All the use cases of CallAnalyzer use the same call site parameter to
both construct the CallAnalyzer, and then pass to the analysis member.
This change removes this duplication.

Reviewers: davidxl, eraman, Jim

Reviewed By: davidxl

Subscribers: Jim, hiraditya, haicheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71645