realtek: make Netgear GS1xx u-boot env partition writable

Make the u-boot environment partition for the NETGEAR
GS108T v3 and GS110TPP writable (they share a DTS), so
the values can be manipulated from userspace.

See https://forum.openwrt.org/t/57875/1567 for a real
world example.

Signed-off-by: Stijn Segers <foss@volatilesystems.org>
(cherry picked from commit 9c381d3386)

target/linux/realtek/dts-5.10/rtl8380_netgear_gigabit_1xx.dtsi

@@ -24,7 +24,6 @@
 			partition@e0000 {
 				label = "u-boot-env";
 				reg = <0x00e0000 0x0010000>;
-				read-only;
 			};
 
 			partition@f0000 {