drm: rcar-du: Refactor DEFR8 feature

Rename the feature from RCAR_DU_FEATURE_DEFR8 to
RCAR_DU_FEATURE_EXT_CTRL_REGS to cover all extended control registers in
addition to the DEFR8 register.

Usage of the feature is refactored to optimize runtime operation and
prepare for external clock support.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_drv.h b/drivers/gpu/drm/rcar-du/rcar_du_drv.h
index 0a72466..c5b9ea6a 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_drv.h
+++ b/drivers/gpu/drm/rcar-du/rcar_du_drv.h
@@ -27,7 +27,7 @@
 struct rcar_du_lvdsenc;
 
 #define RCAR_DU_FEATURE_CRTC_IRQ_CLOCK	(1 << 0)	/* Per-CRTC IRQ and clock */
-#define RCAR_DU_FEATURE_DEFR8		(1 << 1)	/* Has DEFR8 register */
+#define RCAR_DU_FEATURE_EXT_CTRL_REGS	(1 << 1)	/* Has extended control registers */
 
 #define RCAR_DU_QUIRK_ALIGN_128B	(1 << 0)	/* Align pitches to 128 bytes */
 #define RCAR_DU_QUIRK_LVDS_LANES	(1 << 1)	/* LVDS lanes 1 and 3 inverted */