As the EDID property blob may be lost at time after we perform the
detection probe (as the kernel may recreate the EDID blob at any time with
a new id), presume that if there is no matching property that we can
simply keep using the last known EDID.
References: https://bugs.freedesktop.org/show_bug.cgi?id=92728
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>