msm: Make iommu domains platform devices

Information about the layout of iommu domains is a device
specific option. Convert the iommu domain information
into a platform driver with a corresponding platform device.
This allows different devices to have different layouts as
needed.

Change-Id: I6bf4162476143daabe16a2f5de3b655ae4377902
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>