video: sunxi_display: Convert to DM_VIDEO

DM_VIDEO migration deadline is already expired, but around
80 Allwinner boards are still using video in a legacy way:

===================== WARNING ======================
This board does not use CONFIG_DM_VIDEO Please update
the board to use CONFIG_DM_VIDEO before the v2019.07 release.
Failure to update by the deadline may result in board removal.
See doc/driver-model/migration.rst for more info.
====================================================

Convert the legacy video driver over to the DM_VIDEO framework. This is
a minimal conversion: it doesn't use the DT for finding its resources,
nor does it use DM clocks or DM devices for the outputs (LCD, HDMI, CVBS).

Tested in Bananapi M1+ Plus 1920x1200 HDMI out. (Jagan)

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
[Andre: rebase and smaller fixes]
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Simon Glass <sjg@chromium.org>