iommu/arm-smmu-v3: Reduce contention during command-queue insertion

mainline inclusion
from mainline-v5.4-rc1
commit 587e6c10
category: bugfix
bugzilla: 21306
CVE: NA

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The SMMU command queue is a bottleneck in large systems, thanks to the
spin_lock which serialises accesses from all CPUs to the single queue
supported by the hardware.

Attempt to improve this situation by moving to a new algorithm for
inserting commands into the queue, which is lock-free on the fast-path.
Tested-by: NGanapatrao Kulkarni  <gkulkarni@marvell.com>
Signed-off-by: NWill Deacon <will@kernel.org>
Conflicts:
	drivers/iommu/arm-smmu-v3.c
Signed-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>