drm: rcar-du: Add HDMI encoder and connector support

SoCs that integrate the DU have no internal HDMI encoder, support
external encoders only.

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

diff --cc drivers/gpu/drm/rcar-du/Kconfig
Simple merge

diff --cc drivers/gpu/drm/rcar-du/Makefile
Simple merge

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_hdmicon.c
Simple merge

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

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

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

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