message: Fix AffineExpr::simplifyAdd bug
  fix missing check while simplifying an expression with floordiv to a
  mod
  fixes issue
  Closes
  COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/84 from bondhugula:quickfix
diff: @@ -341,7 +341,7 @@ static AffineExpr simplifyAdd(AffineExpr lhs, AffineExpr rhs) {
  // Process lrhs, which is 'expr floordiv c'.
  AffineBinaryOpExpr lrBinOpExpr = lrhs.dyn_cast<AffineBinaryOpExpr>();
  - if (!lrBinOpExpr)
  + if (!lrBinOpExpr || lrBinOpExpr.getKind() != AffineExprKind::FloorDiv)
  return nullptr;
  auto llrhs = lrBinOpExpr.getLHS();
  