iommu: arm-smmu: Add hibernation support for slave-side secure devices

Some targets restrict HLOS access to certain iommu context banks.
Previously these context banks were indicated by the client driver by
setting the IOMMU_DOMAIN_ATTR_SECURE_VMID property. However, the iommu
driver may require this knowledge at probe time, before all client drivers
are available. Therfore pass this information as a devicetree flag.

Additionally, add ops for hibernation.

Change-Id: I2abf9beaa0d17315f0b9399889cd89f0afd8bb7e
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>