dt-binding: ipmi: add fallback to npcm845 compatible

Add to npcm845 KCS compatible string a fallback to npcm750 KCS compatible
string becuase NPCM845 and NPCM750 BMCs are using identical KCS modules.

Fixes: 84261749 ("dt-bindings: ipmi: Add npcm845 compatible")
Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Message-Id: <20220808075452.115907-1-tmaimon77@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>