ath79: correct ar71xx boardname for UniFi AC Lite

This corrects the additional boardname for the image metadata to the one
used in ar71xx. The previously present additional entry was never used
on a running system.

Reviewed-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 1a256470e7)
Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/ath79/image/generic-ubnt.mk

@@ -173,7 +173,7 @@ endef
 define Device/ubnt_unifiac-lite
   $(Device/ubnt_unifiac)
   DEVICE_TITLE := Ubiquiti UniFi AC-Lite
-  SUPPORTED_DEVICES += ubnt-unifiac-lite
+  SUPPORTED_DEVICES += unifiac-lite
 endef
 TARGET_DEVICES += ubnt_unifiac-lite