arm64: dts: add description for solidrun cn9130 som and clearfog boards

Add description for the SolidRun CN9130 SoM, and Clearfog Base / Pro
reference boards.

The SoM has been designed as a pin-compatible replacement for the older
Armada 388 based SoM. Therefore it supports the same boards and a
similar feature set.

Most notable upgrades:
- 4x Cortex-A72
- 10Gbps SFP
- Both eMMC and SD supported at the same time

The developer first supporting this product at SolidRun decided to use
different filenames for the DTBs: Armada 388 uses the full
"clearfog" string while cn9130 uses the abbreviation "cf".
This name is already hard-coded in pre-installed vendor u-boot and can
not be changed easily.

NOTICE IN CASE ANYBODY WANTS TO SELF-UPGRADE:
CN9130 SoM has a different footprint from Armada 388 SoM.
Components on the carrier board below the SoM may collide causing
damage, such as on Clearfog Base.

Signed-off-by: Josua Mayer <josua@solid-run.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>