[XRay][AArch64] More staging for tail call support in XRay on AArch64 - in LLVM

Summary:
This patch prepares more for tail call support in XRay. Until the logging part supports tail calls, this is just staging, so it seems LLVM part is mostly ready with this patch.
Related: https://reviews.llvm.org/D28948 (compiler-rt)

Reviewers: dberris, rengolin

Reviewed By: dberris

Subscribers: llvm-commits, iid_iunknown, aemerson

Differential Revision: https://reviews.llvm.org/D28947

llvm-svn: 293080