arm64: dts: ti: Add support for J7200 Common Processor Board

Add support for J7200 Common Processor Board.
The EVM architecture is very similar to J721E as follows:

+------------------------------------------------------+
|   +-------------------------------------------+      |
|   |                                           |      |
|   |        Add-on Card 1 Options              |      |
|   |                                           |      |
|   +-------------------------------------------+      |
|                                                      |
|                                                      |
|                     +-------------------+            |
|                     |                   |            |
|                     |   SOM             |            |
|  +--------------+   |                   |            |
|  |              |   |                   |            |
|  |  Add-on      |   +-------------------+            |
|  |  Card 2      |                                    |    Power Supply
|  |  Options     |                                    |    |
|  |              |                                    |    |
|  +--------------+                                    | <---
+------------------------------------------------------+
                                Common Processor Board

Common Processor board is the baseboard that has most of the actual
connectors, power supply etc. A SOM (System on Module) is plugged on
to the common processor board and this contains the SoC, PMIC, DDR and
basic high speed components necessary for functionality.

Note:
* The minimum configuration required to boot up the board is System On
  Module(SOM) + Common Processor Board.
* Since there is just a single SOM and Common Processor Board, we are
  maintaining common processor board as the base dts and SOM as the dtsi
  that we include. In the future as more SOM's appear, we should move
  common processor board as a dtsi and include configurations as dts.
* All daughter cards beyond the basic boards shall be maintained as
  overlays.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20200914162231.2535-6-lokeshvutla@ti.com