acpi_video: Intel video is not always i915

Stop it poking at random registers on the i740 cards that may be out there
still.

As per Matthew's feedback remove the conditional checks and never enable the
opregion handling unless an appropriate driver has been loaded.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>