realtek: zyxel-xs1930: fill partition gap with reserved2

The existing partition definition leaves a 640k gap in the flash space,
which makes it harder than necessary to examine or backup those contents.

This commit adds a "reserved2" partition in that gap.

Signed-off-by: Russell Senior <russell@personaltelco.net>
Link: https://github.com/openwrt/openwrt/pull/25241
Signed-off-by: Jonas Jelonek <jonas@jonasjelonek.de>

target/linux/realtek/dts/rtl9313_zyxel_xs1930.dtsi

@@ -157,6 +157,12 @@
 				};
 			};
 
+			partition@1e0000 {
+				label = "reserved2";
+				reg = <0x1e0000 0xa0000>;
+				read-only;
+			};
+
 			/* BootBase has dual-image support. Second partition starts at
 			 * 0x1280000 and has same layout as first partition but smaller size
 			 */