drm/i915/bios: Define VBT block 4 (Mode Support List) contents

Define the contents of VBT block 4 (Mode Support List).

Slightly crazy layout with a variable length list at the start,
followed by the length of said list.

No real idea what these "Intel mode numbers" really are. What
I see in real world VBTs seems to be always the same list of
26 numbers, ranging between 0x30 and 0x84.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-11-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_vbt_defs.h

@@ -571,6 +571,15 @@ struct bdb_display_toggle {
 	u16 list[];						/* ALM only */
 } __packed;
 
+/*
+ * Block 4 - Mode Support List
+ */
+
+struct bdb_mode_support_list {
+	u8 intel_mode_number[0];
+	u16 mode_list_length;
+} __packed;
+
 /*
  * Block 9 - SRD Feature Block
  */