gpu: ion: tegra: Remove unused tegra specific IOMMU definitions

IOMMU related definitions should not be specific to any SoCs.

Change-Id: Ifa47b99d3f66762d75bba92247786ca4cef14c28
Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Reviewed-on: http://git-master/r/73608
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>