Revert "[fximporter] Avoid importing from _torchMlir (#3685)"

This reverts commit 2960538.

python/torch_mlir/extras/fx_importer.py

@@ -135,6 +135,7 @@
     func as func_dialect,
 )
 
+from .._mlir_libs._torchMlir import get_int64_max, get_int64_min
 
 __all__ = [
     "FxImporter",
@@ -1185,9 +1186,9 @@ def set_symbolic_guards(
         def _sympy_int_to_int(val: sympy.Expr, adjust_func: Callable):
             # Convert simple sympy Integers into concrete int
             if val in infs:
-                return torch.iinfo(torch.int64).max
+                return get_int64_max()
             if val in tuple(-inf for inf in infs):
-                return torch.iinfo(torch.int64).min
+                return get_int64_min()
             if isinstance(val, sympy.Integer):
                 return int(val)
             # TODO: Remove this adjustment when fractional ranges are removed