iommu: set the default iommu-dma mode as non-strict

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4K6DE


CVE: NA

The non-strict smmu mode has significant performance gains and can
resolve the nvme soft lockup problem. We enable it by default.

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Currently, many peripherals are faster than before. For example, the top
speed of the older netcard is 10Gb/s, and now it's more than 25Gb/s. But
when iommu page-table mapping enabled, it's hard to reach the top speed
in strict mode, because of frequently map and unmap operations. In order
to keep abreast of the times, I think it's better to set non-strict as
default.

Below it's our iperf performance data of 25Gb netcard:
strict mode: 18-20 Gb/s
non-strict mode: 23.5 Gb/s

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>