arm64: dts: renesas: white-hawk-cpu: Add PCA9654 I/O Expander

Describe the PCA9654 I/O Expander on the White Hawk CPU board.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/e75ea6feaedc013c504a032a6cf1cb7dd809ce27.1664369170.git.geert+renesas@glider.be