gpu: drm: sti: Adopt SPDX identifiers

Add SPDX identifiers to files under sti directory

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Acked-by: Vincent Abriou <vincent.abriou@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171206112947.9569-2-benjamin.gaignard@st.com

drm: sti: add HQVDP plane

High Quality Video Data Plane is hardware IP dedicated
to video rendering. Compare to GPD (graphic planes) it
have better scaler capabilities.

HQVDP use VID layer to push data into hardware compositor
without going into DDR. From data flow point of view HQVDP
and VID are nested so HQVPD update/disable VID.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>