[MPS] Make sure it doesn't break torch < 1.12 (#425)

* [MPS] Make sure it doesn't break torch < 1.12

* up

src/diffusers/testing_utils.py

@@ -5,10 +5,15 @@ from distutils.util import strtobool
 
 import torch
 
+from packaging import version
+
 
 global_rng = random.Random()
 torch_device = "cuda" if torch.cuda.is_available() else "cpu"
-torch_device = "mps" if torch.backends.mps.is_available() else torch_device
+is_torch_higher_equal_than_1_12 = version.parse(version.parse(torch.__version__).base_version) >= version.parse("1.12")
+
+if is_torch_higher_equal_than_1_12:
+    torch_device = "mps" if torch.backends.mps.is_available() else torch_device
 
 
 def parse_flag_from_env(key, default=False):