iommu/io-pgtable: Add a domain attribute for pagetable configuration

Add a new iommu domain attribute DOMAIN_ATTR_IO_PGTABLE_CFG
for pagetable configuration which initially will be used to
set quirks like for system cache aka last level cache to be
used by client drivers like GPU to set right attributes for
caching the hardware pagetables into the system cache and
later can be extended to include other page table configuration
data.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Link: https://lore.kernel.org/r/9190aa16f378fc0a7f8e57b2b9f60b033e7eeb4f.1606287059.git.saiprakash.ranjan@codeaurora.org
Signed-off-by: Will Deacon <will@kernel.org>