ARM: dts: ast2600-evb: fix board compatible

[ Upstream commit aa5e06208500a0db41473caebdee5a2e81d5a277 ]

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


Signed-off-by: Sasha Levin <sashal@kernel.org>