Revert "iommu/arm-smmu: Add support to disable page-table coherency"

This reverts commit f85843d3 ("iommu/arm-smmu: Add support to disable
page-table coherency")

This change was added in order to allow iommu clients to disable page
table coherency.
However when page table coherency is disabled using this property on an
SMMU which is configured to be IO-coherent the attempts by the page table
code to apply CMOs on page table entries will be ignored because the
device it is using to apply the CMOs, the SMMU device, is IO-coherent.
This can result in the SMMU seeing stale page table entries.

Since this feature doesn't work and no clients are using revert it.

Change-Id: If6881d24722dd7f1a7398caf6cd904cc7f792bde
Signed-off-by: Liam Mark <lmark@codeaurora.org>