drm: Add data transmission order bus flag

The flags indicate whether data is transmitted LSB to MSB or MSB to LSB
on the bus.

The exact meaning is bus-type dependent. For instance, for LVDS buses
the flags indicate whether the seven data bits transmitted in a clock
pulse are sent in normal order (MSB to LSB, slots 0 to 6) or reverse
order (LSB to MSB, slots 6 to 0).
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>

include/drm/drm_connector.h

@@ -224,6 +224,10 @@ struct drm_display_info {
 #define DRM_BUS_FLAG_PIXDATA_POSEDGE	(1<<2)
 /* drive data on neg. edge */
 #define DRM_BUS_FLAG_PIXDATA_NEGEDGE	(1<<3)
+/* data is transmitted MSB to LSB on the bus */
+#define DRM_BUS_FLAG_DATA_MSB_TO_LSB	(1<<4)
+/* data is transmitted LSB to MSB on the bus */
+#define DRM_BUS_FLAG_DATA_LSB_TO_MSB	(1<<5)
 
 	/**
 	 * @bus_flags: Additional information (like pixel signal polarity) for