tmnxPortEtherEgrSchedMode sets the SAP egress scheduler mode. In
'fc-based' mode the prority of all the egress queues across all the
SAPs are considered to determine the next queue to schedule. In
'sap-based' mode the scheduler uses the priority of all the egress
queues in a SAP to determine the next queue to schedule and uses
round-robin scheduling mechanism to schedule each of the SAP