luci.mk: add basic support for ucode sources
luci.mk: add basic support for ucode sources

Add special handling for ucode/ package subdirs, analogeous to luasrc/.

Signed-off-by: Jo-Philipp Wich <bd73d35759d75cc215150d1bbc94f1b1078bee01@mein.io>

openwrt/luci,openwrt/luci,hnyman/luci,hnyman/luci,openwrt/luci,hnyman/luci,openwrt/luci,openwrt/luci,hnyman/luci,hnyman/luci,openwrt/luci,hnyman/luci,hnyman/luci,openwrt/luci,hnyman/luci,openwrt/luci