RDMA/hns: ensure for-loop actually iterates and free's buffers

The current for-loop zeros variable i and only loops once, hence
not all the buffers are free'd.  Fix this by setting i correctly.

Detected by CoverityScan, CID#1463415 ("Operands don't affect result")

Fixes: a5073d6054f7 ("RDMA/hns: Add eq support of hip08")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Yixian Liu <liuyixian@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/hns/hns_roce_hw_v2.c

@@ -4383,7 +4383,7 @@ err_dma_alloc_buf:
 	eq->l0_dma = 0;
 
 	if (mhop_num == 1)
-		for (i -= i; i >= 0; i--)
+		for (i -= 1; i >= 0; i--)
 			dma_free_coherent(dev, buf_chk_sz, eq->buf[i],
 					  eq->buf_dma[i]);
 	else if (mhop_num == 2) {