dt-bindings: ipmi: aspeed,ast2400-kcs-bmc: drop unneeded quotes

Cleanup bindings dropping unneeded quotes. Once all these are fixed,
checking for this can be enabled in yamllint.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Message-Id: <20230609140729.64799-1-krzysztof.kozlowski@linaro.org>
Acked-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Corey Minyard <minyard@acm.org>