ARM: dts: keystone: Add Initial DT support for TI K2G SoC family

ARM: dts: keystone: Add Initial DT support for TI K2G SoC family

K2G is the newest addition of TI's Keystone 2 product family. It is a
single core Cortex A15 and a C66x DSP.

K2G supports standard peripherals such as SPI, UART, MMC and USB 2.0.

Includes two dual-core Programmable Real-time Unit and Industrial
Communication Subsystems (PRU-ICSS).

The technical reference manual for K2G can be found here:
http://www.ti.com/lit/ug/spruhy8/spruhy8.pdf

This device is targeted for a variety of applications which include, but
are not limited to:

Home audio
Professional audio
Industrial Programmable Logic Control

The peripheral nodes that have been included in this patch have been
tested during bring-up. Since all peripherals will not necessarily be
used on all boards, disable all peripherals by default. This allow
the board dts to selectively choose which peripherals it wants to
enable.

This SoC now uses the next generation of power management architecture
with the PM functionality located in a microcontroller embedded in the SOC.

Support for this new PM architecture along with other peripherals will be
added in future patches.

Signed-off-by: Vitaly Andrianov <vitalya@ti.com>
Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>