dma/hisilicon: enhance CQ scan robustness

dma/hisilicon: enhance CQ scan robustness

The CQ (completion queue) descriptors were updated by hardware, and then
scanned by driver to retrieve hardware completion status.

This patch enhances robustness by following:
1. replace while (true) with a finite loop to avoid potential dead loop.
2. check the csq_head field in CQ descriptor to avoid status array
overflows.

Fixes: 2db4f0b82360 ("dma/hisilicon: add data path")
Cc: stable@dpdk.org
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>