iommu: arm-smmu: Make restore of smmu-context runtime detectable

Update the logic to restore smmu-context-bank registers using
an additional 'smmu_restore' flag which is only set during
hibernation restore, which makes the logic runtime along 
with the compile-time hibernation flag.

Change-Id: Ic62442601c9dc7ceff4745fdc70b6dc3f56769d7
Signed-off-by: Vivek Kumar <vivekuma@codeaurora.org>