[NFC][MCA] ZnVer1: Update RegisterFile to identify false dependencies on...

[NFC][MCA] ZnVer1: Update RegisterFile to identify false dependencies on partially written registers.

Summary:
Pretty mechanical follow-up for D49196.

As microarchitecture.pdf notes, "20 AMD Ryzen pipeline",
"20.8 Register renaming and out-of-order schedulers":
  The integer register file has 168 physical registers of 64 bits each.
  The floating point register file has 160 registers of 128 bits each.
"20.14 Partial register access":
  The processor always keeps the different parts of an integer register together.
  ...
  An instruction that writes to part of a register will therefore have a false dependence
  on any previous write to the same register or any part of it.

Reviewers: andreadb, courbet, RKSimon, craig.topper, GGanesh

Reviewed By: GGanesh

Subscribers: gbedwell, llvm-commits

Differential Revision: https://reviews.llvm.org/D49393

llvm-svn: 337676