[ascend] fix memory leak: only datatype, const char* does not release

[hellozmz]

Motivation and Context

修复在华为设备上的内存泄漏问题。

Description

修改之前，模型训练过程有内存泄漏：

修复之后，无内存泄漏问题：

换到 #1346 提交pr

Use cases (Optional)

BC-breaking (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the Contributors.md to create this PR.
• Pre-commit or linting tools indicated in Contributors.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.