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

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.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>