From VESA EDID implementation guide v1.0:
"For EDID version 1 revision 2 or earlier data structures when offset 14h
 bit 7 is set to one, the value of bits 6-0 are undefined, and therefore
 cannot be interpreted to mean anything."

And since EDID 1.4 redefines that bit let's consult it only for
EDID 1.3.

Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190529110204.2384-2-ville.syrjala@linux.intel.comReviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>