arch: nios2: rename 'altr,gpio-bank-width' -> 'altr,ngpio'

There is no more 'altr,gpio-bank-width' in the 'altr,pio-1.0' driver.
There is a 'altr,ngpio' which is  what the property wants to configure.

This change updates all occurrences of 'altr,gpio-bank-width' to
'altr,ngpio'.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>

Documentation/devicetree/bindings/fpga/fpga-region.txt

@@ -263,7 +263,7 @@ Overlay contains:
 			gpio@10040 {
 				compatible = "altr,pio-1.0";
 				reg = <0x10040 0x20>;
-				altr,gpio-bank-width = <4>;
+				altr,ngpio = <4>;
 				#gpio-cells = <2>;
 				clocks = <2>;
 				gpio-controller;
@@ -468,7 +468,7 @@ programming is the FPGA based bridge of fpga_region1.
 				compatible = "altr,pio-1.0";
 				reg = <0x10040 0x20>;
 				clocks = <0x2>;
-				altr,gpio-bank-width = <0x4>;
+				altr,ngpio = <0x4>;
 				resetvalue = <0x0>;
 				#gpio-cells = <0x2>;
 				gpio-controller;

arch/nios2/boot/dts/10m50_devboard.dts

@@ -179,7 +179,7 @@ sys_clk_timer: timer@18001440 {
 		led_pio: gpio@180014d0 {
 			compatible = "altr,pio-1.0";
 			reg = <0x180014d0 0x00000010>;
-			altr,gpio-bank-width = <4>;
+			altr,ngpio = <4>;
 			resetvalue = <15>;
 			#gpio-cells = <2>;
 			gpio-controller;
@@ -190,7 +190,7 @@ button_pio: gpio@180014c0 {
 			reg = <0x180014c0 0x00000010>;
 			interrupt-parent = <&cpu>;
 			interrupts = <6>;
-			altr,gpio-bank-width = <3>;
+			altr,ngpio = <3>;
 			altr,interrupt-type = <2>;
 			edge_type = <1>;
 			level_trigger = <0>;