iommu/arm-smmu: use relaxed accessors where possible

Apart from fault handling and page table manipulation, we don't care
about memory ordering between SMMU control registers and normal,
cacheable memory, so use the _relaxed I/O accessors wherever possible.

Change-Id: Ic2e0a1d88f648c9205a0ea31c5e6fefdd4f976bf
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 25724841dfaed05f23a3ddaaaed5c9b61ceea7bd
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>