ARM: IOMMU: Tegra20: Add iommu_ops for GART driver

Tegra 20 IOMMU H/W, GART (Graphics Address Relocation Table). This
patch implements struct iommu_ops for GART for the upper IOMMU API.

This H/W module supports only single virtual address space(domain),
and manages a single level 1-to-1 mapping H/W translation page table.

Change-Id: I2f550bf0e14d9f994abdde79b835ddfe815faa5a
Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Reviewed-on: http://git-master/r/75945
Reviewed-by: Rohan Somvanshi <rsomvanshi@nvidia.com>
Tested-by: Rohan Somvanshi <rsomvanshi@nvidia.com>

Conflicts:
	drivers/iommu/Kconfig
	drivers/iommu/Makefile
HACK: gpu: ion: Add support to remap dma address.

Change-Id: Ica835fad10677ce61d812e00bb489034a8b06a36
Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-on: http://git-master/r/76783
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Hiroshi Doyu <hdoyu@nvidia.com>