gpi: Remove deprecated IOMMU apis

Following apis are deprecated and replaced with device
tree properties.
        arm_iommu_create_mapping
        arm_iommu_release_mapping
        arm_iommu_attach_device
        arm_iommu_detach_device.

Change-Id: I303064db78b441fc783ff7470219f349032b6cd5
Signed-off-by: Vipin Deep Kaur <vkaur@codeaurora.org>