md: fix return value of mddev_trylock

A return value of 0 is treaded as successful lock acquisition. In fact, a
return value of 1 means getting the lock successfully.

Link: https://lore.kernel.org/linux-raid/20260127073951.17248-1-xni@redhat.com
Fixes: 9e59d60 ("md: call del_gendisk in control path")
Reported-by: Bart Van Assche <bvanassche@acm.org>
Closes: https://lore.kernel.org/linux-raid/20250611073108.25463-1-xni@redhat.com/T/#mfa369ef5faa4aa58e13e6d9fdb88aecd862b8f2f
Signed-off-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by:  Li Nan <linan122@huawei.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>

Author: XiaoNi87

drivers/md/md.h

@@ -735,8 +735,8 @@ static inline int mddev_trylock(struct mddev *mddev)
 	int ret;
 
 	ret = mutex_trylock(&mddev->reconfig_mutex);
-	if (!ret && test_bit(MD_DELETED, &mddev->flags)) {
-		ret = -ENODEV;
+	if (ret && test_bit(MD_DELETED, &mddev->flags)) {
+		ret = 0;
 		mutex_unlock(&mddev->reconfig_mutex);
 	}
 	return ret;