arm64: dts: Add support for LX2160 Twins board in single configuration

arm64: dts: Add support for LX2160 Twins board in single configuration

Add support for the SolidRun LX2160A Twins board in its single cpu
configuration.

The twins board is designed to host a pair of LX2160A CEX-7 modules,
sharing a single PCI-E connector in multi-host mode.

It may be assembled in two configurations (different assembly options
facilitating signal re-routing), with a single or with dual CEX-7
module. Their marketing names are:

- SolidWAN Single LX2160
- SolidWAN Dual LX2160

Add the single configuration, featuring:
- 8x SFP (1Gbps)
- 8x SFP+ (1/10Gbps)
- PCI-E OCP card connector
- USB-3.0 front-panel header with single port
- microSD
- dual hot-swappable power supplies

Signed-off-by: Josua Mayer <josua@solid-run.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>