drm: rcar-du: Implement support for interlaced modes

Accept interlaced modes on the VGA and HDMI connectors and configure the
hardware accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_regs.h b/drivers/gpu/drm/rcar-du/rcar_du_regs.h
index c3639d1..70fcbc4 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_regs.h
+++ b/drivers/gpu/drm/rcar-du/rcar_du_regs.h
@@ -34,6 +34,7 @@
 #define DSYSR_SCM_INT_NONE	(0 << 4)
 #define DSYSR_SCM_INT_SYNC	(2 << 4)
 #define DSYSR_SCM_INT_VIDEO	(3 << 4)
+#define DSYSR_SCM_MASK		(3 << 4)
 
 #define DSMR			0x00004
 #define DSMR_VSPM		(1 << 28)