Revert "[DDR] Introduce implicit equality check for the source pattern...

Revert "[DDR] Introduce implicit equality check for the source pattern operands with the same name."

This reverts commit 7271c1bc.

This broke the gcc-5 build:

/usr/include/c++/5/ext/new_allocator.h:120:4: error: no matching function for call to 'std::pair<const std::__cxx11::basic_string<char>, mlir::tblgen::SymbolInfoMap::SymbolInfo>::pair(llvm::StringRef&, mlir::tblgen::SymbolInfoMap::SymbolInfo)'
  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
    ^
In file included from /usr/include/c++/5/utility:70:0,
                 from llvm/include/llvm/Support/type_traits.h:18,
                 from llvm/include/llvm/Support/Casting.h:18,
                 from mlir/include/mlir/Support/LLVM.h:24,
                 from mlir/include/mlir/TableGen/Pattern.h:17,
                 from mlir/lib/TableGen/Pattern.cpp:14:
/usr/include/c++/5/bits/stl_pair.h:206:9: note: candidate: template<class ... _Args1, long unsigned int ..._Indexes1, class ... _Args2, long unsigned int ..._Indexes2> std::pair<_T1, _T2>::pair(std::tuple<_Args1 ...>&, std::tuple<_Args2 ...>&, std::_Index_tuple<_Indexes1 ...>, std::_Index_tuple<_Indexes2 ...>)
         pair(tuple<_Args1...>&, tuple<_Args2...>&,
         ^