Fix the bug of samplepgo indirect call promption when type casting of the return value is needed.

Summary: When type casting of the return value is needed, promoteIndirectCall will return the type casting instruction instead of the direct call. This patch changed to return the direct call instruction instead.

Reviewers: davidxl

Reviewed By: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29569

llvm-svn: 294205