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/Kconfig b/drivers/gpio/Kconfig
index aaa152f..82a8bca 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -598,4 +598,11 @@
 	   8-bit gpo expander, all gpo lines are controlled by writing
 	   value into data register.
 
+config TURRIS_OMNIA_MCU
+	bool "Turris Omnia MCU GPIO driver"
+	depends on DM_GPIO
+	default y if TARGET_TURRIS_OMNIA
+	help
+	   Support for GPIOs on MCU connected to Turris Omnia via i2c.
+
 endif