[ThinLTO] Correct linkonce_any function import linkage. NFC.

Summary:
This is a NFC as we do not import non-odr vague linkage when computing
for import list for a module.

Reviewers: tejohnson, pcc

Subscribers: inglorion, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D54928

llvm-svn: 347763