memory: tegra: Register SMMU after MC driver became ready

Memory Controller driver invokes SMMU driver registration and MC's
registers mapping is shared with SMMU. This mapping goes away if MC
driver probing fails after SMMU registration.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>