iommu/tegra: gart: Integrate with Memory Controller driver

The device-tree binding has been changed. There is no separate GART device
anymore, it is squashed into the Memory Controller. Integrate GART module
with the MC in a way it is done for the SMMU on Tegra30+.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>