drm/i915/bios: add VBT swing bit to child device definition

New bit to look in another BDB block for more. No functional changes.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/7ab46e3f53fd2c12cb60b9eabbebb65b27004a9e.1559308269.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_vbt_defs.h

@@ -391,7 +391,8 @@ struct child_device_config {
 			u8 lspcon:1;				/* 192 */
 			u8 iboost:1;				/* 196 */
 			u8 hpd_invert:1;			/* 196 */
-			u8 flag_reserved:3;
+			u8 use_vbt_vswing:1;			/* 218 */
+			u8 flag_reserved:2;
 			u8 hdmi_support:1;			/* 158 */
 			u8 dp_support:1;			/* 158 */
 			u8 tmds_support:1;			/* 158 */