dt-bindings: bluetooth: reference serial-peripheral-props.yaml

dt-bindings: bluetooth: reference serial-peripheral-props.yaml

Reference common serial properties schema (for children of UART
controllers) to bring common definition of "current-speed" and
"max-speed" properties.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240811-dt-bindings-serial-peripheral-props-v1-5-1dba258b7492@linaro.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>