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;
 			};