[upstream_ut] test_grad_scaling_state_dict_xpu: _scale is not torch.FloatTensor on XPU

## Description
test_grad_scaling_state_dict_xpu in test/test_torch.py fails. The test asserts
that GradScaler._scale is a torch.FloatTensor, but on XPU the scale tensor is
not an instance of torch.FloatTensor (CPU float storage type).

## Error log
```
File "test/test_torch.py", line 5649, in test_grad_scaling_state_dict
self.assertTrue(isinstance(s1._scale, torch.FloatTensor))
AssertionError: False is not true
```

## Reproduce
```
python test/test_torch.py TestTorchDeviceTypeXPU.test_grad_scaling_state_dict_xpu
```