GPIO: fxl6408: Add support for FXL6408 GPIO expander

Initial support for Fairchild's 8 bit I2C gpio expander FXL6408.
The CONFIG_FXL6408_GPIO define enables support for such devices.

Based on: https://patchwork.kernel.org/patch/9148419/

Signed-off-by: Oleksandr Suvorov <cryosay@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@foundries.io>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 3eb77f5..63e9be6 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -16,6 +16,7 @@
 obj-$(CONFIG_ATMEL_PIO4)	+= atmel_pio4.o
 obj-$(CONFIG_BCM6345_GPIO)	+= bcm6345_gpio.o
 obj-$(CONFIG_CORTINA_GPIO)      += cortina_gpio.o
+obj-$(CONFIG_FXL6408_GPIO)	+= gpio-fxl6408.o
 obj-$(CONFIG_INTEL_GPIO)	+= intel_gpio.o
 obj-$(CONFIG_INTEL_ICH6_GPIO)	+= intel_ich6_gpio.o
 obj-$(CONFIG_INTEL_BROADWELL_GPIO)	+= intel_broadwell_gpio.o