Fix：环境为GPU时，无法使用CPU

[xiangking]

Environment info

Python 3.8.10
ark-nlp 0.0.6

### Information

设置cpu无法生效

model = Task(dl_module, optimizer, 'lsce', device='cpu')

[xiangking]

将'ark_nlp.factory.task.base._task.Task'中的初始化方法

if device is None:
    if torch.cuda.is_available():
        if cuda_device == -1:
            self.device = torch.device("cuda")
        else:
            self.device = torch.device(f"cuda:{cuda_device}")
    else:
        self.device = "cpu"

改为

self.device = device 

if self.device is None:
    if torch.cuda.is_available():
        if cuda_device == -1:
            self.device = torch.device("cuda")
        else:
            self.device = torch.device(f"cuda:{cuda_device}")
    else:
        self.device = "cpu"