[SystemZ] Add missing classes and instructions

Summary:
Add instruction formats E, RSI, SSd, SSE, and SSF.

Added BRXH, BRXLE, PR, MVCK, STRAG, and ECTG instructions to test out
those formats.

Reviewers: uweigand

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23179

llvm-svn: 277822