Add ubootenv uci config for GL.inet GL-AR150 Signed-off-by: Kimmo Vuorinen <kimmo.vuorinen@gmail.com> [commit title/message facelift] Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de> (cherry picked from commit a8723c48add5cc8381d88234b9cdda2bb6a866aa)