[libunwind][MIPS]: Rename Registers_mips_n64 to Registers_mips_newabi.

This is in preparation for adding support for N32 unwinding which reuses
the newabi register class.

Reviewed By: compnerd

Differential Revision: https://reviews.llvm.org/D41842


git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@322093 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed