cxgb4: Fix return value check in cfg_queues_uld()

Fix the retrn value check which testing the wrong variable
in cfg_queues_uld().

Fixes: 94cdb8bb

 ("cxgb4: Add support for dynamic allocation of
resources for ULD")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>