gpio: new driver to work with a 8x12 siox

This driver controls a SIOX device that provides 20 I/O lines. The first
twelve are fixed inputs, the remaining eight are outputs.

Acked-by: Gavin Schenk <g.schenk@eckelmann.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -429,6 +429,14 @@ config GPIO_REG
 	  A 32-bit single register GPIO fixed in/out implementation.  This
 	  can be used to represent any register as a set of GPIO signals.
 
+config GPIO_SIOX
+	tristate "SIOX GPIO support"
+	depends on SIOX
+	select GPIOLIB_IRQCHIP
+	help
+	  Say yes here to support SIOX I/O devices. These are units connected
+	  via a SIOX bus and have a number of fixed-direction I/O lines.
+
 config GPIO_SPEAR_SPICS
 	bool "ST SPEAr13xx SPI Chip Select as GPIO support"
 	depends on PLAT_SPEAR