dt-bindings: arm: aspeed: add ASRock Rack ALTRAD8 board

dt-bindings: arm: aspeed: add ASRock Rack ALTRAD8 board

Document ASRock Rack ALTRAD8 (ALTRAD8UD-1L2T and ALTRAD8UD2-1L2Q)
compatibles.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Tan Siewert <tan.siewert@hetzner.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20251218161816.38155-2-rebecca@bsdio.com
[arj: Drop erroneous Tested-by tag from Tan]
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>