realtek: add support for HPE 1920-48G (JG927A) and 1920-48G-PoE (JG928A)

realtek: add support for HPE 1920-48G (JG927A) and 1920-48G-PoE (JG928A)

Hardware information:
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- SoC: RTL8393M
- Copper phy: 6×RTL8218B
- Fibre phy: RTL8214FC
- Flash: 32MiB SPI NOR, MX25L25635FMI
- RAM: 128MiB DDR3, Micron MT41K64M16TW-107
- Serial port: ±5V serial port to RJ45, ZT3232 (MAX3232 compatible)
- +370W POE on JG928A model

Note: SFP ports currently non-functional due to missing support for
RTL8214FC on the RTL8393M target.

Updated for Linux 6.6 kernel.

Installation:
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- Initial installation follows same process as HPE 1920-24G (JG924A)

- Based on prior work of Jan Hoffmann <jan@3e8.eu>
- Additional work by Andreas Böhler <dev@aboehler.at>
- PoE updates and tidy-up by Stephen Howell <howels@allthatwemight.be>
Signed-off-by: Stephen Howell <howels@allthatwemight.be>