realtek: enable pca953x driver for rtl838x subtarget

The system status LED on Panasonic Switch-M8eG PN28080K is connected to
a PCA9539PW. To use the LED as a status LED of OpenWrt while booting,
enable the pca953x driver and built-in to the kernel.
Also enable CONFIG_GPIO_PCA953X_IRQ to use interrupt via RTL83xx GPIO.

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Acked-by: Sander Vanheule <sander@svanheule.net>

target/linux/realtek/rtl838x/config-5.10

@@ -69,6 +69,8 @@ CONFIG_GENERIC_TIME_VSYSCALL=y
 CONFIG_GPIOLIB=y
 CONFIG_GPIOLIB_IRQCHIP=y
 CONFIG_GPIO_GENERIC=y
+CONFIG_GPIO_PCA953X=y
+CONFIG_GPIO_PCA953X_IRQ=y
 CONFIG_GPIO_REALTEK_OTTO=y
 CONFIG_GPIO_RTL8231=y
 CONFIG_GRO_CELLS=y
@@ -166,6 +168,7 @@ CONFIG_REALTEK_OTTO_WDT=y
 CONFIG_REALTEK_PHY=y
 CONFIG_REALTEK_SOC_PHY=y
 CONFIG_REGMAP=y
+CONFIG_REGMAP_I2C=y
 CONFIG_REGMAP_MMIO=y
 CONFIG_RESET_CONTROLLER=y
 CONFIG_RTL83XX=y