iommu/arm-smmu: Invoke pm_runtime across the driver

Enable pm-runtime on devices that implement a pm domain. Then,
add pm runtime hooks to several iommu_ops to power cycle the
smmu device for explicit TLB invalidation requests, and
register space accesses, etc.
We need these hooks when the smmu, linked to its master through
device links, has to be powered-up without the master device
being in context.

Signed-off-by: Sricharan R <sricharan@codeaurora.org>
[vivek: Cleanup pm runtime calls]
Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>