RDMA/cma: Remove NULL check before dev_{put, hold}

The call netdev_{put, hold} of dev_{put, hold} will check NULL, so there
is no need to check before using dev_{put, hold}, remove it to silence the
warning:

./drivers/infiniband/core/cma.c:4812:2-9: WARNING: NULL check before dev_{put, hold} functions is not needed.

Link: https://lore.kernel.org/r/20230614014328.14007-1-yang.lee@linux.alibaba.comReported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5521Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/cma.c

@@ -4805,8 +4805,7 @@ static void cma_make_mc_event(int status, struct rdma_id_private *id_priv,
 	event->param.ud.qkey = id_priv->qkey;
 
 out:
-	if (ndev)
-		dev_put(ndev);
+	dev_put(ndev);
 }
 
 static int cma_ib_mc_handler(int status, struct ib_sa_multicast *multicast)