Skip some relocations in scanRelocs.

When a tls access is optimized, a group of relocations is converted at a
time.

We were already skipping relocations that were optimized out in
relocate, but not in scanRelocs.

This is a small optimization. I got here while working on a patch that
will always keep scanRelocs and relocate in sync.

llvm-svn: 264048
2 files changed