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 --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
index c96f608..2324a52 100644
--- a/drivers/gpu/drm/rcar-du/Kconfig
+++ b/drivers/gpu/drm/rcar-du/Kconfig
@@ -11,10 +11,17 @@
 	  Choose this option if you have an R-Car chipset.
 	  If M is selected the module will be called rcar-du-drm.
 
+config DRM_RCAR_HDMI
+	bool "R-Car DU HDMI Encoder Support"
+	depends on DRM_RCAR_DU
+	depends on OF
+	help
+	  Enable support for external HDMI encoders.
+
 config DRM_RCAR_LVDS
 	bool "R-Car DU LVDS Encoder Support"
 	depends on DRM_RCAR_DU
 	depends on ARCH_R8A7790 || ARCH_R8A7791 || COMPILE_TEST
 	help
-	  Enable support the R-Car Display Unit embedded LVDS encoders
-	  (currently only on R8A7790).
+	  Enable support for the R-Car Display Unit embedded LVDS encoders
+	  (currently only on R8A7790 and R8A7791).