ARM: dts: ast2600-evb: fix board compatible

The AST2600 EVB board should have dedicated compatible.

Fixes: 2ca5646b ("ARM: dts: aspeed: Add AST2600 and EVB")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220529104928.79636-5-krzysztof.kozlowski@linaro.org

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

@@ -8,7 +8,7 @@
 
 / {
 	model = "AST2600 EVB";
-	compatible = "aspeed,ast2600";
+	compatible = "aspeed,ast2600-evb-a1", "aspeed,ast2600";
 
 	aliases {
 		serial4 = &uart5;