drm/edid: restore some type safety to cea_db_*() functions

During the transition, we accepted a void pointer for a poor C
programmer's version of polymorphism. Switch the functions to use struct
cea_db * to regain some more type safety.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c6ad496cdadea1bb598711a65ef536f4a43b74a7.1651569697.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -4384,11 +4384,8 @@ struct cea_db {
 	u8 data[];
 } __packed;
 
-static int cea_db_tag(const void *_db)
+static int cea_db_tag(const struct cea_db *db)
 {
-	/* FIXME: Transition to passing struct cea_db * everywhere. */
-	const struct cea_db *db = _db;
-
 	return db->tag_length >> 5;
 }
 
@@ -4555,47 +4552,47 @@ static void cea_db_iter_end(struct cea_db_iter *iter)
 	memset(iter, 0, sizeof(*iter));
 }
 
-static bool cea_db_is_hdmi_vsdb(const void *db)
+static bool cea_db_is_hdmi_vsdb(const struct cea_db *db)
 {
 	return cea_db_is_vendor(db, HDMI_IEEE_OUI) &&
 		cea_db_payload_len(db) >= 5;
 }
 
-static bool cea_db_is_hdmi_forum_vsdb(const void *db)
+static bool cea_db_is_hdmi_forum_vsdb(const struct cea_db *db)
 {
 	return cea_db_is_vendor(db, HDMI_FORUM_IEEE_OUI) &&
 		cea_db_payload_len(db) >= 7;
 }
 
-static bool cea_db_is_microsoft_vsdb(const void *db)
+static bool cea_db_is_microsoft_vsdb(const struct cea_db *db)
 {
 	return cea_db_is_vendor(db, MICROSOFT_IEEE_OUI) &&
 		cea_db_payload_len(db) == 21;
 }
 
-static bool cea_db_is_vcdb(const void *db)
+static bool cea_db_is_vcdb(const struct cea_db *db)
 {
 	return cea_db_is_extended_tag(db, CTA_EXT_DB_VIDEO_CAP) &&
 		cea_db_payload_len(db) == 2;
 }
 
-static bool cea_db_is_hdmi_forum_scdb(const void *db)
+static bool cea_db_is_hdmi_forum_scdb(const struct cea_db *db)
 {
 	return cea_db_is_extended_tag(db, CTA_EXT_DB_HF_SCDB) &&
 		cea_db_payload_len(db) >= 7;
 }
 
-static bool cea_db_is_y420cmdb(const void *db)
+static bool cea_db_is_y420cmdb(const struct cea_db *db)
 {
 	return cea_db_is_extended_tag(db, CTA_EXT_DB_420_VIDEO_CAP_MAP);
 }
 
-static bool cea_db_is_y420vdb(const void *db)
+static bool cea_db_is_y420vdb(const struct cea_db *db)
 {
 	return cea_db_is_extended_tag(db, CTA_EXT_DB_420_VIDEO_DATA);
 }
 
-static bool cea_db_is_hdmi_hdr_metadata_block(const void *db)
+static bool cea_db_is_hdmi_hdr_metadata_block(const struct cea_db *db)
 {
 	return cea_db_is_extended_tag(db, CTA_EXT_DB_HDR_STATIC_METADATA) &&
 		cea_db_payload_len(db) >= 3;