mbuf: fix struct initialization with C++

g++ reports "error: missing initializer for member"

Fixes: 5d3f72100904 ("mbuf: implement generic format for sched field")

Signed-off-by: Ed Czeck <ed.czeck@atomicrules.com>

lib/librte_mbuf/rte_mbuf.h

@@ -2464,6 +2464,7 @@ rte_mbuf_sched_set(struct rte_mbuf *m, uint32_t queue_id,
 				.queue_id = queue_id,
 				.traffic_class = traffic_class,
 				.color = color,
+				.reserved = 0,
 			};
 }