Enable FP8 on rocm for gfx12

### Feature Idea

gfx12 (9060, 9070) brings support for fp8 on AMD consumer cards. This functionality is currently soldered off, I think by comfy/model_management.py, if not other parts of the codebase:

```py
def supports_fp8_compute(device=None):
if not is_nvidia():
return False
```

fp8 should be enabled on these platforms, and other AMD cards that support it.

### Existing Solutions

_No response_

### Other

_No response_