iommu: arm-smmu: Add hibernation callbacks to pm_ops

Add required callbacks(thaw and restore), to pm_ops for
hibernation to function properly. arm-smmu driver has
to be restored before any dependent client drivers are
restored. Hence use early variant callbacks.

Change-Id: I3f3dba5753e0b0efe1e32fd3d16fc4373574efa5
Signed-off-by: Omkar Savagaonkar <omkars@codeaurora.org>