Now the EDID property will be updated when the corresponding EDID can be
obtained from the external display device. But after the external device
is plugged-out, the EDID property is not updated. In such case we still
get the corresponding EDID property although it is already detected as
disconnected.

https://bugs.freedesktop.org/show_bug.cgi?id=26743



Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>