Log level change from ERR to INFO for fetch systemports issue (#1632)

SAI attribute SAI_SWITCH_ATTR_NUMBER_OF_SYSTEM_PORTS is not supported on many platforms, and the call to getSystemPorts() throws error.
This error is not harmful at this state, and therefore the log level is changed from ERROR to INFO.

orchagent/portsorch.cpp

@@ -4848,7 +4848,7 @@ bool PortsOrch::getSystemPorts()
     status = sai_switch_api->get_switch_attribute(gSwitchId, 1, &attr);
     if (status != SAI_STATUS_SUCCESS)
     {
-        SWSS_LOG_ERROR("Failed to get number of system ports, rv:%d", status);
+        SWSS_LOG_INFO("Failed to get number of system ports, rv:%d", status);
         return false;
     }