Fix build by disabling per-feed repos again

Updating OpenWrt accidentally enabled this option.

include/config

@@ -1,3 +1,6 @@
+CONFIG_IMAGEOPT=y
+# CONFIG_PER_FEED_REPO is not set
+
 CONFIG_BUSYBOX_CUSTOM=y
 CONFIG_BUSYBOX_CONFIG_SHA512SUM=y
 # CONFIG_BUSYBOX_CONFIG_FEATURE_PREFER_IPV4_ADDRESS is not set