arch: nios2: remove 'resetvalue' property

The 'altr,pio-1.0' driver does not handle the 'resetvalue', so remove it.
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

@@ -469,7 +469,6 @@ programming is the FPGA based bridge of fpga_region1.
 				reg = <0x10040 0x20>;
 				clocks = <0x2>;
 				altr,ngpio = <0x4>;
-				resetvalue = <0x0>;
 				#gpio-cells = <0x2>;
 				gpio-controller;
 			};

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

@@ -180,7 +180,6 @@ led_pio: gpio@180014d0 {
 			compatible = "altr,pio-1.0";
 			reg = <0x180014d0 0x00000010>;
 			altr,ngpio = <4>;
-			resetvalue = <15>;
 			#gpio-cells = <2>;
 			gpio-controller;
 		};
@@ -194,7 +193,6 @@ button_pio: gpio@180014c0 {
 			altr,interrupt-type = <2>;
 			edge_type = <1>;
 			level_trigger = <0>;
-			resetvalue = <0>;
 			#gpio-cells = <2>;
 			gpio-controller;
 		};