drm/i915/bios: Define VBT block 55 (RGB Palette Table) contents

Define the contents of VBT block 55 (RGB Palette Table).

Note that I've not actually seen any real world VBTs with this
block.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-31-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -182,6 +182,7 @@ enum bdb_block_id {
 	BDB_FIXED_SET_MODE		= 51, /* 172+ */
 	BDB_MIPI_CONFIG			= 52, /* 175+ */
 	BDB_MIPI_SEQUENCE		= 53, /* 177+ */
+	BDB_RGB_PALETTE			= 54, /* 180+ */
 	BDB_COMPRESSION_PARAMETERS	= 56, /* 213+ */
 	BDB_GENERIC_DTD			= 58, /* 229+ */
 	BDB_SKIP			= 254, /* VBIOS only */
@@ -1418,6 +1419,17 @@ struct bdb_mipi_sequence {
 	u8 data[]; /* up to 6 variable length blocks */
 } __packed;
 
+/*
+ * Block 55 - RGB Palette Table
+ */
+
+struct bdb_rgb_palette {
+	u8 is_enabled;
+	u8 red[256];
+	u8 blue[256];
+	u8 green[256];
+} __packed;
+
 /*
  * Block 56 - Compression Parameters
  */