As part of the grand SMMU driver refactoring effort, the I/O register
accessors were moved into 'arm-smmu.h' in commit 6d7dff62
("iommu/arm-smmu: Move Secure access quirk to implementation").

On 32-bit architectures (such as ARM), the 64-bit accessors are defined
in 'linux/io-64-nonatomic-hi-lo.h', so include this header to fix the
build.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>