drm/i915/bios: Define VBT block 253 (PRD Table) contents

Define the contents of VBT block 253 (PRD Table).

Unfortunately the block has two definitions, with the cutoff
supposedly happening on ICL vs. TGL. Also according to some
notes it might be that the VBIOS (if that's still a thing)
still uses the old definition even on TGL+. Quite the mess.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-36-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -189,6 +189,7 @@ enum bdb_block_id {
 	BDB_VSWING_PREEMPH		= 57, /* 218+ */
 	BDB_GENERIC_DTD			= 58, /* 229+ */
 	BDB_INT15_HOOK			= 252, /* VBIOS only */
+	BDB_PRD_TABLE			= 253,
 	BDB_SKIP			= 254, /* VBIOS only */
 };
 
@@ -1571,4 +1572,29 @@ struct bdb_generic_dtd {
 	struct generic_dtd_entry dtd[];	/* up to 24 DTD's */
 } __packed;
 
+/*
+ * Block 253 - PRD Table
+ */
+
+struct prd_entry_old {
+	u8 displays_attached;
+	u8 display_in_pipe_a;
+	u8 display_in_pipe_b;
+} __packed;
+
+struct bdb_prd_table_old {
+	struct prd_entry_old list[0];				/* ???-216 */
+	u16 num_entries;					/* ???-216 */
+} __packed;
+
+struct prd_entry_new {
+	u16 primary_display;
+	u16 secondary_display;
+} __packed;
+
+struct bdb_prd_table_new {
+	u16 num_entries;					/* 217+ */
+	struct prd_entry_new list[];				/* 217+ */
+} __packed;
+
 #endif /* _INTEL_VBT_DEFS_H_ */