arm64: dts: mediatek: cherry: Add support for internal eMMC storage

Add mtk-sd controller and pin configuration to enable the internal
eMMC storage: now it is possible to mount a rootfs located at the
internal storage.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20220704101321.44835-6-angelogioacchino.delregno@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>