ramips: fix Xiaomi MiWiFi Nano firmware partition size

Even the commit message of the patch adding support for the MiWiFi Nano
says that a 16 MB flash chip is used. Extend the firmware partition to
make use of all available flash space.

Fixes: FS#622

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ramips/dts/MIWIFI-NANO.dts

@@ -98,7 +98,7 @@
 
 		partition@50000 {
 			label = "firmware";
-			reg = <0x50000 0x7b0000>;
+			reg = <0x50000 0xfb0000>;
 		};
 	};
 };