gpio: Add viperboard gpio driver

This adds the mfd cell to use the gpio a and gpio b part
of the Nano River Technologies viperboard.

Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/mfd/viperboard.h

@@ -44,6 +44,8 @@
 #define VPRBRD_USB_TIMEOUT_MS       100
 #define VPRBRD_USB_REQUEST_MAJOR    0xea
 #define VPRBRD_USB_REQUEST_MINOR    0xeb
+#define VPRBRD_USB_REQUEST_GPIOA    0xed
+#define VPRBRD_USB_REQUEST_GPIOB    0xdd
 
 struct vprbrd_i2c_write_hdr {
 	u8 cmd;