arm64: tegra: Add the memory subsystem on Tegra194

The memory subsystem on Tegra194 encompasses both the memory and
external memory controllers. The EMC is represented as a subnode of the
MC and a ranges property is used to describe the register ranges.

A dma-ranges property is also added to describe that all memory clients
can address up to 39 bits using the memory controller client interface
(MCCIF), unless otherwise limited by the DMA engines of the hardware. A
memory client can technically use 40 bits of addresses, but the memory
controller on Tegra194 uses bit 39 to determine the XBAR format used to
access memory. Use of this bit needs to be explicitly controlled by the
operating system drivers for devices that can use this on-the-fly format
conversion. Using the dma-ranges property prevents the operating system
from using the bit implicitly, for example in I/O virtual address
mappings.

Signed-off-by: Thierry Reding <treding@nvidia.com>