dt-bindings: memory: mediatek,smi: Update condition for mt8195 smi node

The max clock items for the dts node with compatible
'mediatek,mt8195-smi-sub-common' should be 3.

However, the dtbs_check of such node will get following message,
arch/arm64/boot/dts/mediatek/mt8195-evb.dtb: smi@14010000: clock-names: ['apb', 'smi', 'gals0'] is too long
         From schema: Documentation/devicetree/bindings/memory-controllers/mediatek,smi-common.yaml

It's because the 'mediatek,mt8195-smi-sub-common' compatible incorrectly
matches the 'else' conditions for gen2 HW without gals.

Rewrite the 'else' condition to specifically identify the compatibles
that utilizing gen2 HW without gals.

Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220729063208.16799-3-tinghan.shen@mediatek.com