### What this PR does / why we need it?
According to issue
https://github.com/vllm-project/vllm-ascend/issues/1298 ,this pull
request adds unit test code for platform.py.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
CI passed with new added/existing test.
- vLLM version: v0.10.1.1
- vLLM main:
b5d34af328
---------
Signed-off-by: zhanghaiwen <zhanghaiwen@cmss.chinamobile.com>
Co-authored-by: zhanghaiwen <zhanghaiwen@cmss.chinamobile.com>