[QoS]Test_buffer_model test skip for Nokia platform (sonic-net#13690)

What is the motivation for this PR?
Test suite was executing skipped test.

How did you do it?
Updated the conditional mark skip condition

How did you verify/test it?
Executed the test and verify the results

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -1318,7 +1318,7 @@ qos/test_buffer.py::test_buffer_model_test:
     reason: "Running only on mellanox devices and covered by unit testing / M0/MX topo does not support qos"
     conditions_logical_operator: or
     conditions:
-      - "asic_type in ['mellanox']"
+      - "asic_type in ['mellanox'] or asic_subtype in ['broadcom-dnx']"
       - "topo_type in ['m0', 'mx']"
 
 qos/test_buffer_traditional.py: