bugfix: fix unittest test_fp8_quantize (#1599)

<!-- .github/pull_request_template.md -->

## 📌 Description

test_fp8_quantize unittest is broken by #1446 because we didn't check
the special case of cpu input.
This PR fixes the issue.

## 🔍 Related Issues

<!-- Link any related issues here -->

## 🚀 Pull Request Checklist

Thank you for contributing to FlashInfer! Before we review your pull
request, please make sure the following items are complete.

### ✅ Pre-commit Checks

- [x] I have installed `pre-commit` by running `pip install pre-commit`
(or used your preferred method).
- [x] I have installed the hooks with `pre-commit install`.
- [x] I have run the hooks manually with `pre-commit run --all-files`
and fixed any reported issues.

> If you are unsure about how to set up `pre-commit`, see [the
pre-commit documentation](https://pre-commit.com/).

## 🧪 Tests

- [x] Tests have been added or updated as needed.
- [x] All tests are passing (`unittest`, etc.).

## Reviewer Notes

<!-- Optional: anything you'd like reviewers to focus on, concerns, etc.
-->

Author: yzh119

flashinfer/utils.py

@@ -513,6 +513,8 @@ def set_log_level(lvl_str: str) -> None:
 
 
 def device_support_pdl(device: torch.device) -> bool:
+    if device.type != "cuda":
+        return False
     major, _ = get_compute_capability(device)
     return major >= 9