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

arch/arm/configs/shmobile_defconfig

@@ -89,6 +89,7 @@ CONFIG_PINCTRL_RZA1=y
 CONFIG_PINCTRL_RZA2=y
 CONFIG_GPIO_EM=y
 CONFIG_GPIO_RCAR=y
+CONFIG_GPIO_PCA953X=y
 CONFIG_GPIO_PCF857X=y
 CONFIG_POWER_RESET=y
 CONFIG_POWER_RESET_RMOBILE=y