ARM: shmobile: defconfig: Enable CAT9554 support

Enable support for the ON Semiconductor CAT9554 I2C I/O Expander, which
is used on the RSK+RZA1 board.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200624131931.3686-4-geert+renesas@glider.be