ARM: dts: marzen: Enable I2C support

Enable the single I2C bus available on the Marzen development board.
As this bus contains an AK4643 codec, it must be limited to 100 kHz.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/77b87378397fd26f39c73f68e3ea465db6d38fb1.1679330016.git.geert+renesas@glider.be