[SWDEV-489696] Improve AMD SMI Python APIs Functional and Unit Testing (#468)

* Adding python unit tests
* Remove duplicate functions definitions
* Added missing classes for __init__ for py-interface

---------

Signed-off-by: josnarlo <Joseph.Narlo@amd.com>
Signed-off-by: Maisam Arif <Maisam.Arif@amd.com>

src/amd_smi/amd_smi.cc

@@ -3303,7 +3303,9 @@ amdsmi_status_t amdsmi_get_gpu_reg_table_info(
 }
 
 void amdsmi_free_name_value_pairs(void *p) {
-    free(p);
+    if (p)
+        free(p);
+    return;
 }
 
 amdsmi_status_t