[ppc] Distinguish the 'es', 'o', 'm', 'Q', 'Z', and 'Zy' inline assembly memory constraints.

Summary:
But still handle them the same way since I don't know how they differ on
this target.

Of these, 'es', and 'Q' do not have backend tests but are accepted by
clang.

No functional change intended. Depends on D8173.

Reviewers: hfinkel

Reviewed By: hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8213

llvm-svn: 232466