drm: rcar-du: Add support notification of frame end status

Fix DU driver so that other drivers get the frame-end status of the particular channel.
Additionally, add the interface that notifies the frame-end status.

Not for upstream merge.

Signed-off-by: Sei Fumizono <sei.fumizono.jw@hitachi-solutions.com>
Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>
(cherry picked from commit da36539c99c9af5fb22e09a05cfb2bff8479211a)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
2 files changed