iommu/arm-smmu: support mapping before enabling S1 translations

For performance reasons there are clients who would like to move
from stage 1 bypass to stage 1 enabled without having to stop their
device.

Currently clients need to stop their device because they have to
create the required stage 1 mappings before re-enabling the device.
Add the new DOMAIN_ATTR_EARLY_MAP domain attribute to allow clients
to create stage 1 mappings after attaching but before enabling
stage 1 translations.

If the clients set the DOMAIN_ATTR_EARLY_MAP domain attribute to 1
before attaching then then once they attach the SMMU driver won't
enable stage 1 translations. This gives the client the opportunity to
create the required early mappings (for example using iommu_map).
When the client has finished creating the necessary early mappings
the client can then set the DOMAIN_ATTR_EARLY_MAP domain attribute
to 0, this will in turn enable stage 1 translations.

Change-Id: I9e95c5d2130f1d371e201eac69dec140cc773b1f
Signed-off-by: Liam Mark <lmark@codeaurora.org>