dt-bindings: mmc: mtk-sd: Add support for MT8189 SoC

dt-bindings: mmc: mtk-sd: Add support for MT8189 SoC

Add a new compatible for MMC IP in MT8189 SoC.
Even though this is partially compatible with the one found in MT8196
SoC, the MT8189 SoC register layout has some slight differences and
additional features.

Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>