ARM: shmobile: koelsch: Add DU HDMI output support

Add DT nodes for the ADV7511 HDMI encoder and its HDMI output connector
and configure the DISP pin group that drives the HDMI transmitter DE
pin.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>