Revert "[Thumb] Save/restore high registers in Thumb1 pro/epilogues"

This reverts r283867.

This appears to be an infinite loop:

    while (HiRegToSave != AllHighRegs.end() && CopyReg != AllCopyRegs.end()) {
      if (HiRegsToSave.count(*HiRegToSave)) {
        ...

        CopyReg = findNextOrderedReg(++CopyReg, CopyRegs, AllCopyRegs.end());
        HiRegToSave =
            findNextOrderedReg(++HiRegToSave, HiRegsToSave, AllHighRegs.end());
      }
    }

llvm-svn: 283938