drm/i915: slow acpi_lid_open() causes flickering - V2

acpi_lid_open() could take up to 10ms on my computer.  Some component is
calling the drm GETCONNECTOR ioctl many times in a row.  This results in
flickering (for example, when starting a video).  Fix it by assuming an
always connected lid status.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Eric Anholt <eric@anholt.net>