Revert "[mips] Add names and tests for the hardware registers"

This reverts commit r221299.

The tests

    LLVM :: MC/Disassembler/Mips/mips32.txt
    LLVM :: MC/Disassembler/Mips/mips32_le.txt

were failing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221307 91177308-0d34-0410-b5e6-96231b3b80d8