ARM: STi: DT: add keyscan for stih41x-b2000

Add keyscan setup for stih415/h416 b2000.
Both have same raw/column lines number, debounce time and keymap.

Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Giuseppe Condorelli <giuseppe.condorelli@st.com>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>