Tegra20 doesn't have SMMU. Move out checking of the SMMU presence from
the SMMU driver into the Memory Controller driver. This change makes code
consistent in regards to how GART/SMMU presence checking is performed.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>