gpio: add GPIO support for SMSC SCH311x

This patch adds support for the GPIOs found on the SMSC "Super I/
SCH311x.

The chip detection and I/O functions are copied from sch311x_wdt.

Signed-off-by: Bruno Randolf <br1@einfach.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 02e8d53..f456b93 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -244,6 +244,15 @@
 	  Legacy GPIO support. Use only for platforms without support for
 	  pinctrl.
 
+config GPIO_SCH311X
+	tristate "SMSC SCH311x SuperI/O GPIO"
+	help
+	  Driver to enable the GPIOs found on SMSC SMSC SCH3112, SCH3114 and
+	  SCH3116 "Super I/O" chipsets.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gpio-sch311x.
+
 config GPIO_SPEAR_SPICS
 	bool "ST SPEAr13xx SPI Chip Select as GPIO support"
 	depends on PLAT_SPEAR