Add the HDMI encoder to the R8A77965 DT in disabled state.

Based on a similar patch of the R8A7796 device tree
by Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>.
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[Kieran: Rebase to top of tree]
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>