sched: improve doxygen comments
sched: improve doxygen comments

Improve doxygen comments.

Signed-off-by: Jasvinder Singh <97b766ecf460b59e2781d4fc0469065206870f5c@intel.com>
Signed-off-by: Abraham Tovar <98d3e8b22093d6deae21addaa8419e14f35dcecd@intel.com>
Signed-off-by: Lukasz Krakowiak <c57f1976190d7df21a5b26774cd84e4edecb5a81@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk