Revert "[TableGen] Fix a typo"

Summary:
This reverts commit r360106.

The revisioin causes llvm-tblgen to hang while generating info for
RISCV.td. The root cause might be in the RISCV.td definition but I don't
know enough about this to investigate further.

Command that starts hangning after r360106:
`llvm-build/bin/llvm-tblgen -I llvm/include -I llvm/tools/clang/include -I llvm/lib/Target/RISCV -gen-instr-info llvm/lib/Target/RISCV/RISCV.td`

Reviewers: sammccall, yan_luo, craig.topper, gribozavr

Reviewed By: gribozavr

Subscribers: PkmX, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61632

llvm-svn: 360136