add COM subsystem commanding

eive_tmtc/tmtc/__init__.py

@@ -1,3 +1,3 @@
-from .payload.pl_subsystem import add_payload_subsystem_cmds
+from .payload.subsystem import add_payload_subsystem_cmds
 from .solar_array_deployment import add_sa_depl_cmds
 from .test import add_test_defs