dt-bindings: mmc: uniphier-sd: Add socionext,syscon-uhs-mode property

UHS mode control is included in the interface logic represented
by syscon. To refer this, add new property "socionext,syscon-uhs-mode".

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230125010201.28246-2-hayashi.kunihiko@socionext.com


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