gpio: add TS-5500 DIO blocks support

Technologic Systems TS-5500 provides digital I/O lines exposed through
pin blocks. On this platform, there are three of them, named DIO1, DIO2
and LCD port, that may be used as a DIO block.

The TS-5500 pin blocks are described in the product's wiki:
http://wiki.embeddedarm.com/wiki/TS-5500#Digital_I.2FO

This driver is not limited to the TS-5500 blocks. It can be extended to
support similar boards pin blocks, such as on the TS-5600.

This patch is the V2 of the previous https://lkml.org/lkml/2012/9/25/671
with corrections suggested by Linus Walleij.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Jerome Oufella <jerome.oufella@savoirfairelinux.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -211,6 +211,14 @@ config GPIO_STA2X11
 	  Say yes here to support the STA2x11/ConneXt GPIO device.
 	  The GPIO module has 128 GPIO pins with alternate functions.
 
+config GPIO_TS5500
+	tristate "TS-5500 DIO blocks and compatibles"
+	help
+	  This driver supports Digital I/O exposed by pin blocks found on some
+	  Technologic Systems platforms. It includes, but is not limited to, 3
+	  blocks of the TS-5500: DIO1, DIO2 and the LCD port, and the TS-5600
+	  LCD port.
+
 config GPIO_VT8500
 	bool "VIA/Wondermedia SoC GPIO Support"
 	depends on ARCH_VT8500

drivers/gpio/Makefile

@@ -71,6 +71,7 @@ obj-$(CONFIG_ARCH_DAVINCI_TNETV107X) += gpio-tnetv107x.o
 obj-$(CONFIG_GPIO_TPS6586X)	+= gpio-tps6586x.o
 obj-$(CONFIG_GPIO_TPS65910)	+= gpio-tps65910.o
 obj-$(CONFIG_GPIO_TPS65912)	+= gpio-tps65912.o
+obj-$(CONFIG_GPIO_TS5500)	+= gpio-ts5500.o
 obj-$(CONFIG_GPIO_TWL4030)	+= gpio-twl4030.o
 obj-$(CONFIG_GPIO_TWL6040)	+= gpio-twl6040.o
 obj-$(CONFIG_GPIO_UCB1400)	+= gpio-ucb1400.o