ARM: dts: aspeed: centriq2400: drop the board

The board is unmaintained and unused, according to Joel, so simply let's
remove it.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/all/CACPK8XfxXi8kQr+vxta8rD6SBgxLf_oBjAH0UkPBacQta552YQ@mail.gmail.com/
Link: https://lore.kernel.org/r/20220623072428.33697-1-krzysztof.kozlowski@linaro.org

'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>