drm/edid: cleanup patch for CEA extended-tag macro

CEA-861-F introduces extended tag codes for EDID extension blocks,
which indicates the actual type of the data block. The code for
using exteded tag is 0x7, whereas in the existing code, the
corresponding macro is named as "VIDEO_CAPABILITY_BLOCK"

This patch renames the macro and usages from "VIDEO_CAPABILITY_BLOCK"
to "USE_EXTENDED_TAG"

V2: Add extended tag code check for video capabilitiy block (ville)
V3: Ville:
	- Use suggested names for macros
	- Check the block length first, before checking the extended tag
V4: Fix commit message (David)
V5: Introduced this patch into HDMI-YCBCR-output series
V6: Rebase
V7: Rebase

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1499960000-9232-5-git-send-email-shashank.sharma@intel.comSigned-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/drm_edid.c

@@ -2781,7 +2781,8 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 #define VIDEO_BLOCK     0x02
 #define VENDOR_BLOCK    0x03
 #define SPEAKER_BLOCK	0x04
-#define VIDEO_CAPABILITY_BLOCK	0x07
+#define USE_EXTENDED_TAG 0x07
+#define EXT_VIDEO_CAPABILITY_BLOCK 0x00
 #define EDID_BASIC_AUDIO	(1 << 6)
 #define EDID_CEA_YCRCB444	(1 << 5)
 #define EDID_CEA_YCRCB422	(1 << 4)
@@ -3441,6 +3442,12 @@ cea_db_payload_len(const u8 *db)
 	return db[0] & 0x1f;
 }
 
+static int
+cea_db_extended_tag(const u8 *db)
+{
+	return db[1];
+}
+
 static int
 cea_db_tag(const u8 *db)
 {
@@ -4017,8 +4024,10 @@ bool drm_rgb_quant_range_selectable(struct edid *edid)
 		return false;
 
 	for_each_cea_db(edid_ext, i, start, end) {
-		if (cea_db_tag(&edid_ext[i]) == VIDEO_CAPABILITY_BLOCK &&
-		    cea_db_payload_len(&edid_ext[i]) == 2) {
+		if (cea_db_tag(&edid_ext[i]) == USE_EXTENDED_TAG &&
+		    cea_db_payload_len(&edid_ext[i]) == 2 &&
+		    cea_db_extended_tag(&edid_ext[i]) ==
+			EXT_VIDEO_CAPABILITY_BLOCK) {
 			DRM_DEBUG_KMS("CEA VCDB 0x%02x\n", edid_ext[i + 2]);
 			return edid_ext[i + 2] & EDID_CEA_VCDB_QS;
 		}