[DPDK] /lib/eal: fix failed to stop device monitor error

[wenxuanx.wu@intel.com]

From: Wenxuan Wu <wenxuanx.wu@intel.com>

The ret value in rte_dev_event_monitor_stop stands for whether the
monitor has been successfully closed ,and should not bind with
rte_intr_callback_unregister,so once it goes to the right exit point of
rte_dev_event_monitor, the ret value should be set to 0.

Also ,the refmonitor count has been carefully evaluated ,the value
change from 1 to 0 ,so there is no potential memory leak failure.

Fixes: 1fef6ced07f3 ("eal/linux: allow multiple starts of event monitor")
Cc:stable@intel.com

Signed-off-by: Wenxuan Wu <wenxuanx.wu@intel.com>
---
 lib/eal/linux/eal_dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/eal/linux/eal_dev.c b/lib/eal/linux/eal_dev.c
index bde55a3d92..4646e8a550 100644
--- a/lib/eal/linux/eal_dev.c
+++ b/lib/eal/linux/eal_dev.c
@@ -384,6 +384,7 @@ rte_dev_event_monitor_stop(void)
 	close(rte_intr_fd_get(intr_handle));
 	rte_intr_instance_free(intr_handle);
 	intr_handle = NULL;
+	ret = 0;
 
 	monitor_refcount--;
 
-- 
2.25.1