arm64: dts: 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>
Link: https://lore.kernel.org/r/20240419103019.992586-3-amadeus@jmu.edu.cnSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts

@@ -8,7 +8,7 @@
 #include "rk3568.dtsi"
 
 / {
-	model = "Radxa ROCK3 Model A";
+	model = "Radxa ROCK 3A";
 	compatible = "radxa,rock3a", "rockchip,rk3568";
 
 	aliases {