iommu: tegra/smmu: Fix with mainline IOMMU API change

The mainline IOMMU API v3.3-rc1 has been changed so that bytes are
used in mapping size instead of page order and page-by-page iteration
is taken care of by iommu core.

The rest are mostly for maintainability:
$ git co iommu/next drivers/iommu/tegra-smmu.c

Change-Id: Ib4fdee4a637b3065a1eab6c56923b05f46b3b582
Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Reviewed-on: http://git-master/r/78137
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>