[LLDB][PPC64] Fixed issues with expedited registers

Summary:
- reg_nums were missing the end marker entry
- marked FP test to be skipped for ppc64

Reviewers: labath, clayborg

Reviewed By: labath, clayborg

Subscribers: alexandreyy, lbianc, nemanjai, kbarton

Differential Revision: https://reviews.llvm.org/D43767
Patch by Leandro Lupori <leandro.lupori@gmail.com>

llvm-svn: 326775