msm: iommu: Remove dependency on IDR

Remove the depencency on the IOMMU IDR register, as it may
not be accessible depending on the security configuraton.
This involves moving the NCB field of IDR into the platform
data.

Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>