Fix constant propagation pass to consider kwargs (pytorch#4166)

Summary: Pull Request resolved: pytorch#4166

Reviewed By: cccclai, mcremon-meta

Differential Revision: D59345251

fbshipit-source-id: b371df5a24ffdbba2cff2967094860b5b1756b93

Author: Reza Rahimi

exir/passes/constant_prop_pass.py

@@ -4,6 +4,8 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
+# pyre-unsafe
+
 from collections import OrderedDict
 from typing import cast, Mapping, Optional
 
@@ -126,6 +128,10 @@ def get_propagated_const_tensor_dict(
             node.args,
             exported_program,
             const_node_to_tensor,
+        ) or not is_const(
+            node.kwargs,
+            exported_program,
+            const_node_to_tensor,
         ):
             continue