dt-bindings: net: qca,ar9331: convert to DT schema

Convert the Qualcomm Atheros AR9331 built-in switch bindings to DT
schema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20240212182911.233819-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>