dt-bindings: arm: rockchip: correct the model name for Radxa ROCK 3A

According to https://radxa.com/products/rock3/3a

,
the name of this board should be "Radxa ROCK 3A".

Suggested-by: FUKAUMI Naoki <naoki@radxa.com>
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240419103019.992586-2-amadeus@jmu.edu.cn


Signed-off-by: Heiko Stuebner <heiko@sntech.de>