ARM: dts: ast2600-evb: fix board compatible
The AST2600 EVB board should have dedicated compatible.
Fixes: 2ca5646b5c2f ("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