Do not apply redundant LastCallToStaticBonus

Summary:
As written in the comments above, LastCallToStaticBonus is already applied to
the cost if Caller has only one user, so it is redundant to reapply the bonus
here.

If the only user is not a caller, TotalSecondaryCost will not be adjusted
anyway because callerWillBeRemoved is false. If there's no caller at all, we
don't need to care about TotalSecondaryCost because
inliningPreventsSomeOuterInline is false.

Reviewers: chandlerc, eraman

Reviewed By: eraman

Subscribers: haicheng, davidxl, davide, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D29169

llvm-svn: 295075