[package] uboot-env: add config for the ALFA NETWORKS Hornet-UB (AP121U)

Signed-off-by: Daniel Golle <daniel.golle@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt@37382 3c298f89-4303-0410-b956-a3cf2f4a3e73