iommu/arm-smmu: Track context bank state

Echoing what we do for Stream Map Entries, maintain a software shadow
state for context bank configuration. With this in place, we are mere
moments away from blissfully easy suspend/resume support.

Change-Id: Ieb9ee45d31474dbc3f9cb1fa5054f18b1e414a40
Reviewed-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
[will: fix sparse warning by only clearing .cfg during domain destruction]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 90df373cc62e527b010025249d11d10d19b086bd
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[pdaly: Add attributes field. Modify DOMAIN_ATTRIBUTE_EARLY_MAP
handling]
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>