The rcar-du driver refuses connecting an LVDS output to an HDMI encoder.
There is not technical reason for that restriction, remove it.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

SoCs that integrate the DU have no internal HDMI encoder, support
external encoders only.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>