Documentation: Rename gpio controller name from cygnus to iproc

Renamed gpio controller's driver name from cygnus to iproc to make it
more generic so that all iProc based SoCs having the same gpio controller
could use this.
Signed-off-by: NPramod Kumar <pramodku@broadcom.com>
Reviewed-by: NRay Jui <rjui@broadcom.com>
Reviewed-by: NScott Branden <sbranden@broadcom.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt → Documentation/devicetree/bindings/pinctrl/brcm,iproc-gpio.txt

-Broadcom Cygnus GPIO/PINCONF Controller
+Broadcom iProc GPIO/PINCONF Controller
 
 Required properties:
 
@@ -7,7 +7,7 @@ Required properties:
     "brcm,cygnus-crmu-gpio" or "brcm,iproc-gpio"
 
 - reg:
-    Define the base and range of the I/O address space that contains the Cygnus
+    Define the base and range of the I/O address space that contains SoC
 GPIO/PINCONF controller registers
 
 - ngpios: