dt-bindings: arm: realtek: Add Kent Soc family compatibles

dt-bindings: arm: realtek: Add Kent Soc family compatibles

Define compatible strings for Realtek RTD1501s, RTD1861b and RTD1920s.

Additionally, convert legacy DTS-style comments to YAML description
properties, following the pattern from the ARM bindings conversion series
[1].

[1] https://lore.kernel.org/lkml/20200622125527.24207-2-afaerber@suse.de/

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20260127071530.25426-2-eleanor15x@gmail.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>