RDMA/nldev: Add checks for nla_nest_start() in fill_stat_counter_qps()

As the nla_nest_start() may fail with NULL returned, the return value needs
to be checked.

Fixes: c4ffee7c ("RDMA/netlink: Implement counter dumpit calback")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Link: https://lore.kernel.org/r/20221126043410.85632-1-yuancan@huawei.comSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/core/nldev.c

@@ -894,6 +894,8 @@ static int fill_stat_counter_qps(struct sk_buff *msg,
 	int ret = 0;
 
 	table_attr = nla_nest_start(msg, RDMA_NLDEV_ATTR_RES_QP);
+	if (!table_attr)
+		return -EMSGSIZE;
 
 	rt = &counter->device->res[RDMA_RESTRACK_QP];
 	xa_lock(&rt->xa);