gpu: ion: 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.

Change-Id: Ib331b6f3f7075385499eb13dd040c80444d706a8
Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Reviewed-on: http://git-master/r/78139
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>