[Bitcode] Update CHECK-DAG usage in tests

[Bitcode] Update CHECK-DAG usage in tests

This patch adjusts tests not to depend on deprecated FileCheck
behavior that permits overlapping matches within a block of
`CHECK-DAG` directives:

1. `thinlto-function-summary-originalnames.ll`: The directive with the
pattern `<COMBINED` is surely intended to match `<COMBINED ` (note the
trailing space), but it instead matches
`<COMBINED_GLOBALVAR_INIT_REFS`, for which there is a separate
directive.  With the deprecated behavior, both directives match the
latter text and neither match the former text.  I've adjusted the
former directive so it matches only the former text.

2. `thinlto-summary-local-5.0.ll`: Two directives have identical
patterns when they were clearly meant to have different patterns.

3. `upgrade-pointer-address-space.ll`: There are three identical
directives but only two occurrences of the matching text.  With the
deprecated behavior, they always match exactly the same text, so the
behavior can't have been useful.  I removed one of the directives and
converted the other two from `CHECK-DAG` to `CHECK`.

Reviewed By: probinson, aprantl

Differential Revision: https://reviews.llvm.org/D64036

llvm-svn: 365060