RDMA/hns: Clean up the return value check of hns_roce_alloc_cmd_mailbox()

hns_roce_alloc_cmd_mailbox() never returns NULL, so the check should be
IS_ERR(). And the error code should be converted as the function's return
value.

Link: https://lore.kernel.org/r/20220302064830.61706-8-liangwenpeng@huawei.com
Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/hns/hns_roce_hw_v2.c

@@ -5981,8 +5981,8 @@ static int hns_roce_v2_create_eq(struct hns_roce_dev *hr_dev,
 
 	/* Allocate mailbox memory */
 	mailbox = hns_roce_alloc_cmd_mailbox(hr_dev);
-	if (IS_ERR_OR_NULL(mailbox))
-		return -ENOMEM;
+	if (IS_ERR(mailbox))
+		return PTR_ERR(mailbox);
 
 	ret = alloc_eq_buf(hr_dev, eq);
 	if (ret)

drivers/infiniband/hw/hns/hns_roce_mr.c

@@ -148,10 +148,8 @@ static int hns_roce_mr_enable(struct hns_roce_dev *hr_dev,
 
 	/* Allocate mailbox memory */
 	mailbox = hns_roce_alloc_cmd_mailbox(hr_dev);
-	if (IS_ERR(mailbox)) {
-		ret = PTR_ERR(mailbox);
-		return ret;
-	}
+	if (IS_ERR(mailbox))
+		return PTR_ERR(mailbox);
 
 	if (mr->type != MR_TYPE_FRMR)
 		ret = hr_dev->hw->write_mtpt(hr_dev, mailbox->buf, mr);

drivers/infiniband/hw/hns/hns_roce_srq.c

@@ -89,9 +89,9 @@ static int alloc_srqc(struct hns_roce_dev *hr_dev, struct hns_roce_srq *srq)
 	}
 
 	mailbox = hns_roce_alloc_cmd_mailbox(hr_dev);
-	if (IS_ERR_OR_NULL(mailbox)) {
+	if (IS_ERR(mailbox)) {
 		ibdev_err(ibdev, "failed to alloc mailbox for SRQC.\n");
-		ret = -ENOMEM;
+		ret = PTR_ERR(mailbox);
 		goto err_xa;
 	}