Add call branch annotation for ICP promoted direct call in SamplePGO mode.

Summary: SamplePGO uses branch_weight annotation to represent callsite hotness. When ICP promotes an indirect call to direct call, we need to make sure the direct call is annotated with branch_weight in SamplePGO mode, so that downstream function inliner can use hot callsite heuristic.

Reviewers: davidxl, eraman, xur

Reviewed By: davidxl, xur

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D30282

llvm-svn: 296028