ramips: fix 04_led_migration case syntax for mt7621

Commit f761f405 had bogus case syntax, the uci-defaults script threw
errors as a result and exited non-zero, probably didn't do what was
intended, but tried over and over since the non-zero exit prevents the
script from being deleted.

Fixes: f761f405 ("ramips: mt7621: harmonize naming scheme for Mikrotik")

Signed-off-by: Russell Senior <russell@personaltelco.net>
[extend commit title, add Fixes]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/mt7621/base-files/etc/uci-defaults/04_led_migration

@@ -9,14 +9,16 @@ boardonly="${board##*,}"
 case "$board" in
 mikrotik,routerboard-750gr3)
 	migrate_leds "^rb750gr3:=$boardonly:"
+	;;
 mikrotik,routerboard-m11g)
 	migrate_leds "^rbm11g:=$boardonly:"
+	;;
 mikrotik,routerboard-m33g)
 	migrate_leds "^rbm33g:=$boardonly:"
+	;;
 netgear,wndr3700-v5)
 	migrate_leds "^wndr3700v5:=$boardonly:"
 	;;
-
 esac
 
 migrations_apply system