ath79: fix DTS node names for Ubiquiti XW partitions

Some node names were inconsistent with the reg property. Fix it.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit 1a0d6e1eba57d38c5ab6b0e8468188f09e45079d)
[fixed XM->XW in commit title for backport]

target/linux/ath79/dts/ar9342_ubnt_xw.dtsi

@@ -96,13 +96,13 @@
 				reg = <0x050000 0x760000>;
 			};
 
-			partition@fb0000 {
+			partition@7b0000 {
 				label = "cfg";
 				reg = <0x7b0000 0x040000>;
 				read-only;
 			};
 
-			eeprom: partition@ff0000 {
+			eeprom: partition@7f0000 {
 				label = "EEPROM";
 				reg = <0x7f0000 0x010000>;
 				read-only;