arm64: dts: rockchip: Correct the model names for Radxa ROCK 5 boards

Correct the descriptions of a few Radxa boards, according to the up-to-date
documentation from Radxa and the detailed explanation from Naoki. [1]  To sum
it up, the short naming, as specified by Radxa, is preferred.

[1] https://lore.kernel.org/linux-rockchip/B26C732A4DCEA9B3+282b8775-601b-4d4a-a513-4924b7940076@radxa.com/Suggested-by: FUKAUMI Naoki <naoki@radxa.com>
Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/6931289a252dc2d6c7bfd2388835c5e98ba0d8c9.1713457260.git.dsimic@manjaro.orgSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts

@@ -7,7 +7,7 @@
 #include "rk3588.dtsi"
 
 / {
-	model = "Radxa ROCK 5 Model B";
+	model = "Radxa ROCK 5B";
 	compatible = "radxa,rock-5b", "rockchip,rk3588";
 
 	aliases {

arch/arm64/boot/dts/rockchip/rk3588s-rock-5a.dts

@@ -8,7 +8,7 @@
 #include "rk3588s.dtsi"
 
 / {
-	model = "Radxa ROCK 5 Model A";
+	model = "Radxa ROCK 5A";
 	compatible = "radxa,rock-5a", "rockchip,rk3588s";
 
 	aliases {