ARM: dts: ast2500: Add ngpios property to GPIO node

Populate gpio_count in the gpio subsystem for the AST2500.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/arch/arm/dts/ast2500.dtsi b/arch/arm/dts/ast2500.dtsi
index 98359bf..ee66ef6 100644
--- a/arch/arm/dts/ast2500.dtsi
+++ b/arch/arm/dts/ast2500.dtsi
@@ -214,6 +214,7 @@
 				reg = <0x1e780000 0x1000>;
 				interrupts = <20>;
 				gpio-ranges = <&pinctrl 0 0 220>;
+				ngpios = <228>;
 				interrupt-controller;
 			};