gpio: exar: add gpio for exar cards

Exar XR17V352/354/358 chips have 16 multi-purpose inputs/outputs which
can be controlled using gpio interface.

Add the gpio specific code.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 701809b..2d77392 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -185,6 +185,13 @@
 	help
 	  Say yes here to support the GPIO controller on Axis ETRAX FS SoCs.
 
+config GPIO_EXAR
+	tristate "Support for GPIO pins on XR17V352/354/358"
+	depends on SERIAL_8250_EXAR
+	help
+	  Selecting this option will enable handling of GPIO pins present
+	  on Exar XR17V352/354/358 chips.
+
 config GPIO_GE_FPGA
 	bool "GE FPGA based GPIO"
 	depends on GE_FPGA