ARM: DT: STiH410: Add DRM dt nodes

This patch adds the DRM/KMS dt nodes.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@linaro.org>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>