iommu/arm-smmu: Express fastmap domain geometries correctly

Fastmap implicilty imposes a requirement on clients that the
domain geometry must be within the range [0, SZ_4G). The domain
geometry is only adjusted in the presence of the qcom,iommu-dma-addr-pool
property. Otherwise, the SMMU HW's restrictions are imposed on
the domain geometry.

This is problematic for fastmap clients that don't explicilty
express a domain geometry requirement, as the SMMU HW's geometry
restrictions may not align with the fastmap geometry restrictions.

Thus for fastmap clients that do not express domain geometry
requirements, impose the default fastmap domain geometry
requirement. This makes it so that the geometry does not need
to be fixed up for the debug devices, so remove the handling
for that as well.

Change-Id: I66f5fc6e80de621ae80888333126c7bcd3c15775
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>