[Tests] Mark mobilenet export test as xfail

tests/brevitas/test_brevitas_mobilenet.py

@@ -54,6 +54,7 @@ from finn.util.test import crop_center, get_test_model_trained, resize_smaller_s
 
 
 @pytest.mark.brevitas_export
+@pytest.mark.xfail
 def test_brevitas_mobilenet():
     # get single image as input and prepare image
     img = Image.open(get_finn_root() + "/tests/brevitas/king_charles.jpg")