gpio: sx150x: add Semtech I2C sx150x gpio expander driver

Add support for Semtech SX150-series I2C GPIO expanders.  Compatible
models include:

8 bits:  sx1508q
16 bits: sx1509q

Signed-off-by: Gregory Bean <gbean@codeaurora.org>
Cc: David Brownell <david-b@pacbell.net>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Trilok Soni <tsoni@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/Kconfig

@@ -195,6 +195,17 @@ config GPIO_PCF857X
 	  This driver provides an in-kernel interface to those GPIOs using
 	  platform-neutral GPIO calls.
 
+config GPIO_SX150X
+	bool "Semtech SX150x I2C GPIO expander"
+	depends on I2C=y
+	default n
+	help
+	  Say yes here to provide support for Semtech SX150-series I2C
+	  GPIO expanders. Compatible models include:
+
+	  8 bits:  sx1508q
+	  16 bits: sx1509q
+
 config GPIO_TC35892
 	bool "TC35892 GPIOs"
 	depends on MFD_TC35892

drivers/gpio/Makefile

@@ -35,3 +35,4 @@ obj-$(CONFIG_GPIO_WM8994)	+= wm8994-gpio.o
 obj-$(CONFIG_GPIO_SCH)		+= sch_gpio.o
 obj-$(CONFIG_GPIO_RDC321X)	+= rdc321x-gpio.o
 obj-$(CONFIG_GPIO_JANZ_TTL)	+= janz-ttl.o
+obj-$(CONFIG_GPIO_SX150X)	+= sx150x.o