If we try to commit the display list while an update is pending, we have
missed our opportunity. The display list manager will hold the commit
until the next interrupt.

In this event, we skip the pipeline completion callback handler so that
the pipeline will not mistakenly report frame completion to the user.
Signed-off-by: NKieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>