[PT FE] Support aten::softplus (#21367)

* [PT FE] Support aten::softplus

* Fix name

tests/layer_tests/pytorch_tests/test_softplus.py

@@ -0,0 +1,24 @@
+# Copyright (C) 2018-2023 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+import torch
+
+from pytorch_layer_test_class import PytorchLayerTest
+
+
+class aten_softplus(torch.nn.Module):
+    def forward(self, x):
+        return torch.nn.functional.softplus(x)
+
+
+class TestSoftplus(PytorchLayerTest):
+    def _prepare_input(self):
+        import numpy as np
+        return (np.random.randn(2, 4, 224, 224).astype(np.float32),)
+
+    @pytest.mark.nightly
+    @pytest.mark.precommit
+    def test_softplus(self, ie_device, precision, ir_version):
+        self._test(aten_softplus(), None, "aten::softplus",
+                   ie_device, precision, ir_version)