drm: rcar-du: Pass the encoder DT node to rcar_du_encoder_init()

The encoder DT node will be needed to register an external HDMI encoder.
Pass it to the rcar_du_encoder_init() function to prepare for HDMI
support.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

diff --cc drivers/gpu/drm/rcar-du/rcar_du_encoder.c
Simple merge

diff --cc drivers/gpu/drm/rcar-du/rcar_du_encoder.h
Simple merge

diff --cc drivers/gpu/drm/rcar-du/rcar_du_kms.c
Simple merge