dt-bindings: mmc: marvell,xenon-sdhci: Drop requiring 2 clocks

The "axi" clock is optional on at least the "marvell,armada-ap806-sdhci"
variant. Not sure what's correct here, so just drop the constraint.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250320-dt-marvell-mmc-v1-3-e51002ea0238@kernel.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>