ARM: sti: stih416: Enable board LED support for B2020 RevE

There are two LEDs available on the B2020 RevE board, one red, one
green.  In this patch we enable the red one for "heartbeat" and turn
the green one off.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>