RDMA/rtrs-srv-sysfs: fix missing put_device

put_device() decreases the ref-count and then the device will be
cleaned-up, while at is also add missing put_device in
rtrs_srv_create_once_sysfs_root_folders

This patch solves a kmemleak error as below:

  unreferenced object 0xffff88809a7a0710 (size 8):
    comm "kworker/4:1H", pid 113, jiffies 4295833049 (age 6212.380s)
    hex dump (first 8 bytes):
      62 6c 61 00 6b 6b 6b a5                          bla.kkk.
    backtrace:
      [<0000000054413611>] kstrdup+0x2e/0x60
      [<0000000078e3120a>] kobject_set_name_vargs+0x2f/0xb0
      [<00000000f1a17a6b>] dev_set_name+0xab/0xe0
      [<00000000d5502e32>] rtrs_srv_create_sess_files+0x2fb/0x314 [rtrs_server]
      [<00000000ed11a1ef>] rtrs_srv_info_req_done+0x631/0x800 [rtrs_server]
      [<000000008fc5aa8f>] __ib_process_cq+0x94/0x100 [ib_core]
      [<00000000a9599cb4>] ib_cq_poll_work+0x32/0xc0 [ib_core]
      [<00000000cfc376be>] process_one_work+0x4bc/0x980
      [<0000000016e5c96a>] worker_thread+0x78/0x5c0
      [<00000000c20b8be0>] kthread+0x191/0x1e0
      [<000000006c9c0003>] ret_from_fork+0x3a/0x50

Fixes: baa5b28b7a ("RDMA/rtrs-srv: Replace device_register with device_initialize and device_add")
Link: https://lore.kernel.org/r/20210212134525.103456-5-jinpu.wang@cloud.ionos.com
Signed-off-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-srv-sysfs.c

@@ -183,6 +183,7 @@ static int rtrs_srv_create_once_sysfs_root_folders(struct rtrs_srv_sess *sess)
 		err = -ENOMEM;
 		pr_err("kobject_create_and_add(): %d\n", err);
 		device_del(&srv->dev);
+		put_device(&srv->dev);
 		goto unlock;
 	}
 	dev_set_uevent_suppress(&srv->dev, false);
@@ -208,6 +209,7 @@ rtrs_srv_destroy_once_sysfs_root_folders(struct rtrs_srv_sess *sess)
 		kobject_put(srv->kobj_paths);
 		mutex_unlock(&srv->paths_mutex);
 		device_del(&srv->dev);
+		put_device(&srv->dev);
 	} else {
 		mutex_unlock(&srv->paths_mutex);
 	}