ARM: dts: ast2600-evb-a1: fix board compatible

The AST2600 EVB A1 board should have dedicated compatible.

Fixes: a7295518 ("ARM: dts: aspeed: ast2600evb: Add dts file for A1 and A0")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220529104928.79636-6-krzysztof.kozlowski@linaro.org

arch/arm/boot/dts/aspeed-ast2600-evb-a1.dts

@@ -5,6 +5,7 @@
 
 / {
 	model = "AST2600 A1 EVB";
+	compatible = "aspeed,ast2600-evb-a1", "aspeed,ast2600";
 
 	/delete-node/regulator-vcc-sdhci0;
 	/delete-node/regulator-vcc-sdhci1;