Refactor code so model can be a dtype other than fp32 or fp16.

comfy/model_management.py

@@ -448,6 +448,11 @@ def unet_inital_load_device(parameters, dtype):
     else:
         return cpu_dev
 
+def unet_dtype(device=None, model_params=0):
+    if should_use_fp16(device=device, model_params=model_params):
+        return torch.float16
+    return torch.float32
+
 def text_encoder_offload_device():
     if args.gpu_only:
         return get_torch_device()