drm/stm: ltdc: add per plane update support

drm/stm: ltdc: add per plane update support

Recent ltdc hardware versions offer the ability
to update a plane independently of others planes.
This is could be useful especially if a plane is
assigned to another OS.

Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215214817.20310-1-yannick.fertre@foss.st.com