gpio: Add Turris Omnia MCU driver

This driver registers GPIO controller and allows U-Boot to control GPIO
pins on MCU which is connected to Turris Omnia via i2c.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index d755276..219f37e 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -75,3 +75,4 @@
 obj-$(CONFIG_SL28CPLD_GPIO)	+= sl28cpld-gpio.o
 obj-$(CONFIG_ZYNQMP_GPIO_MODEPIN)	+= zynqmp_gpio_modepin.o
 obj-$(CONFIG_SLG7XL45106_I2C_GPO)	+= gpio_slg7xl45106.o
+obj-$(CONFIG_$(SPL_TPL_)TURRIS_OMNIA_MCU)	+= turris_omnia_mcu.o