iommu: msm: secure: support attributes which clients use

Some IOMMU client drivers expect certain attributes to
be available. Present MSM IOMMU driver really don't deal
with them. But clients don't really care what IOMMU driver
does behind the doors. For ex.
DOMAIN_ATTR_COHERENT_HTW_DISABLE is really not enabled
for secure MSM driver. So, just let clients calm down
by providing dummy support for those attributes.

Change-Id: I5cc1874d194f3d001f29aee1a9ff72e510ae16bd
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>