dt-binding: Add ngpios property to GPIO controller node

Add ngpios property to the gpio controller's DT node so that controller
driver extracts total number of in-use gpio lines from DT and removes
dependency on driver.
Signed-off-by: Pramod Kumar <pramodku@broadcom.com>
Reviewed-by: Ray Jui <rjui@broadcom.com>
Reviewed-by: Scott Branden <sbranden@broadcom.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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

@@ -10,6 +10,9 @@ Required properties:
     Define the base and range of the I/O address space that contains the Cygnus
 GPIO/PINCONF controller registers
 
+- ngpios:
+    Total number of in-use slots in GPIO controller
+
 - #gpio-cells:
     Must be two. The first cell is the GPIO pin number (within the
 controller's pin space) and the second cell is used for the following:
@@ -57,6 +60,7 @@ Example:
 		compatible = "brcm,cygnus-ccm-gpio";
 		reg = <0x1800a000 0x50>,
 		      <0x0301d164 0x20>;
+		ngpios = <24>;
 		#gpio-cells = <2>;
 		gpio-controller;
 		interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
@@ -78,6 +82,7 @@ Example:
 	gpio_asiu: gpio@180a5000 {
 		compatible = "brcm,cygnus-asiu-gpio";
 		reg = <0x180a5000 0x668>;
+		ngpios = <146>;
 		#gpio-cells = <2>;
 		gpio-controller;
 		interrupts = <GIC_SPI 174 IRQ_TYPE_LEVEL_HIGH>;