Intel graphics hardware that implements the ACPI IGD OpRegion spec
requires that the list of display devices be populated before any ACPI
video methods are called. Detect when this is the case and defer
registration until the opregion code calls it. Fixes crashes on HP
laptops.

http://bugzilla.kernel.org/show_bug.cgi?id=11259Signed-off-by: NMatthew Garrett <mjg@redhat.com>
Acked-by: NEric Anholt <eric@anholt.net>
Signed-off-by: NLen Brown <len.brown@intel.com>