sched: fix build without red

sched: fix build without red

This commit fixes the following compile error messages when
CONFIG_RTE_SCHED_RED=n and CONFIG_RTE_SCHED_COLLECT_STATS=y;

rte_sched.c: In function ‘rte_sched_port_update_subport_stats_on_drop’:
rte_sched.c:1090:41: error: unused parameter ‘red’
		struct rte_mbuf *pkt, uint32_t red)
                                         ^
rte_sched.c: In function ‘rte_sched_port_update_queue_stats_on_drop’:
rte_sched.c:1116:39: error: unused parameter ‘red’
		struct rte_mbuf *pkt, uint32_t red)

Fixes: 4d51afb5cdb6 ("sched: keep track of RED drops")

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>