[XCOFF] emit .rename for .lcomm when necessary

Summary:

This is a follow up for D82481. For .lcomm directive, although it's
not necessary to have .rename emitted, it's still desirable to do
it so that we do not see internal 'Rename..' gets print out in
symbol table. And we could have consistent naming between TC entry
and .lcomm. And also have consistent naming between IR and final
object file.

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D86075